Pretreatment

Keywords: Modified alkaline hydrogen peroxide pretreatment Lignin removal Enzymatic hydrolysis Simultaneous saccharification and fermentation A B S T R A C T To overcome the typical delignification saturation point of alkaline peroxide pretreatment and further facilitate lignin removal, a novel modified alkaline hydrogen peroxide pretreatment (MAHP) was proposed by introducing ethanol into the reaction system. The dosages of H 2 O 2 , ethanol, and pretreatment temperature were optimized, and the results revealed that a maximum lignin removal as high as 79.25% could be achieved at only 100 • C, 3 wt % H 2 O 2 concentration and 1 wt% ethanol concentration. Meanwhile, 76.5% of glucan and 56.0% of xylan were preserved at this pretreatment condition. By overcoming the delignification saturation point, enzymatic hy-drolysis efficiency was remarkably enhanced, achieving 96.76% and 97.38% of glucan and xylan conversion, respectively, which are 7.4 and 11.4 times as compared to that of the untreated bamboo. Furthermore, the simultaneous saccharification and fermentation (SSF) result indicated an identical ethanol yield of ~75% when elevating the SSF solid loading from 5% to 30%. Based on the sequential SSF and xylose fermentation results, about 5.6 tons of bamboo would be consumed to produce 1 ton of ethanol. Finally, the energy balance revealed that a positive balance of 1255.4 KJ could be generated via processing 1 kg bamboo. The results demonstrate that the MAHP is a promising high-efficiency pretreatment technology for bamboo due to the mild pretreatment severity and robust ethanol yield.

Present work primarily deals with the exhaustive investigations of rapid de-lignification processes from source-sorted organic fractions that are recalcitrant in nature. Organic solid wastes (OSW) belongs to the organic fraction of municipal solid wastes (MSW) and they act as enormous potential substrate for alternative source of energy in the form of bio-fuels. Nevertheless, these substrates are not easily biodegradable and the degree of biodegradability is solely dependent on the composition & characteristic of organic solid wastes in municipal solid wastes. The component responsible for recalcitrance of organic solid wastes is lignin that occurs in variable amounts in different plant residues. In order to remove the recalcitrance from organic fraction municipal solid wastes and to make it more easily degradable by microbial consortia, certain pretreatment techniques have been adopted and they are applied either individually or in combined way for enhancement of bio-methanation i....

Agro by-products can be sustainable feedstock for the production of various versatile bio-products. The pre-treatment of which is needed for optimal utilization of recalcitrant lignocellulosic biomass. This study investigated the effect of various acids and alkalis on the pre-treatment of rice husks to make it suitable for use in fermentation. Dry rice husks with the weight of 10 g were pre-treated with 1 % (w/v) of five acids and two alkalis with water loading of 10 ml/g of rice husks. The rice husks that was pre-treated with 1 % (w/v) nitric acid produced the highest total reducing sugars in the hydrolyzate (approximately 4.2 mg/ g of rice husks) after 8 hours at 100 oC followed by pre-treatment with acetic acid (~0.7 mg) and sodium hydroxide (~0.4 mg). Hydrolysis with other acids and alkali produced less than 0.1 mg reducing sugars/ g rice husks. In conclusion, nitric acid was found to be the best hydrolyzing reagent for pre-treatment of rice husks in this study.

Deep eutectic solvents (DESs) are an emerging class of mixtures characterized by significant depressions in melting points compared to those of the neat constituent components. These materials are promising for applications as inexpensive "designer" solvents exhibiting a host of tunable physicochemical properties. A detailed review of the current literature reveals the lack of predictive understanding of the microscopic mechanisms that govern the structure−property relationships in this class of solvents. Complex hydrogen bonding is postulated as the root cause of their melting point depressions and physicochemical properties; to understand these hydrogen bonded networks, it is imperative to study these systems as dynamic entities using both simulations and experiments. This review emphasizes recent research efforts in order to elucidate the next steps needed to develop a fundamental framework needed for a deeper understanding of DESs. It covers recent developments in DES research, frames outstanding scientific questions, and identifies promising research thrusts aligned with the advancement of the field toward predictive models and fundamental understanding of these solvents. CONTENTS

In the first journal in the desalination world, Desalination, during the last 20 years, there is the birth of a new seawater pretreatment process: electrocoagulation (EC). In order to note some facts of this birth, relate its context, and understand its circumstances, this review concerns a brief description of the application of EC as a new seawater pretreatment process throughout the work of Sanfan and Qinlai (1987) until the work of Yi et al. (2009) via the work of Sanfan (1991); all of them are published in Desalination. The first paper (1987) discusses the mechanism of removing some ions from the brackish water using EC method. Experiment results present some major parameters for the EC process. The most important one in operation is electric current density (CD). Moreover, the first paper suggests the method of selecting optimum density
and some ways could raise economic property of EC and could reduce handling costs. In the paper of Sanfan (1991) the further research results of improving economic property of EC
method are discussed. In order to reduce the cost and raise the handling efficiency, five different technological processes are set up and studied. The best one was the using Fe electrode
and aerating for raw water combine with reusing flocs. It can reduce 60% of handling cost in comparison withal electrode and remove 75% of hardness. Finally, Yi et al. (2009) use a simple and new effective electrochemical method (EM) prior to reverse osmosis for seawater desalination. The influences of three main factors in EMs—CD, operating time and sedimentation time on the efficiency of pretreatment—have been investigated. It is shown that the EM is very effective
for removal of turbidity. The qualities of the raw and the treated seawater have been measured using UV–Vis spectrometry. The morphologies and the particle size distribution of the resulted sludge have been characterised by scanning electron microscopy (SEM) and a particle size analyser, and the mechanism of the EM has been analysed theoretically. Raw seawater with a turbidity of 54.1 NTU, 94.48 mg L−1 SS after EM pretreatment at 26.30 mA cm−2 CD for 40 min reduces the turbidity to 1.00 NTU. The time taken for the same depletion of turbidity in case of 39.45 mA cm−2 CD is 35 min, and the absorbance of the curve decreases when EM treatment is applied. The experimental results reveal that particular size in seawater agglomerate and get bigger after EM treatment, and the turbidity removal is enhanced by charge neutralisation and sweep coagulation. The sludge generated from the process is found to have larger specific surface
areas at higher CD from SEM observation, leading to better treatment efficiency.

Pretreatment process is the key technological step in lignocellulose bioconversion into biofuel owing to its robust molecular structure. This pivotal process can markedly affect the overall sustainability of lignocellulosic biofuel systems because of its energy-intensive, chemical-dependent, and time-consuming nature. More advanced methods should then be developed to evaluate the effects of pretreatment methods on the thermodynamic, economic, and environmental features of lignocellulosic biofuel systems. Among the various tools developed so far, exergetic approaches have attracted a great deal of interest for decision-making purposes because of their interdisciplinary character. Exergy-based methods could provide invaluable information regarding the technical characteristics, economic costs, and environmental impacts of lignocellulosic biofuel systems. Hence, this review is aimed at briefly summarizing the lignocellulose pretreatment methods as well as comprehensively reviewing and critically discussing their key effects on the exergetic aspects of the resulting biofuels. Overall, the hotspots of thermodynamic inefficiency, cost loss, and environmental burden of lignocellulosic biofuel systems could be reliably identified using exergetic methods. Much of the current literature on exergetic analysis of the lig-nocellulose pretreatment process has been particularly limited to dilute sulfuric acid, organosolv, and steam explosion pretreatment methods, while exergetic aspects of alkaline, liquid hot water, biological, and combined approaches have not been evaluated well enough. In addition, the majority of the published works have only focused on quantifying thermodynamic imperfections and determining exergetic efficiencies of the simulation-based lignocellulosic biofuel systems, while a limited number of studies have investigated exergy-based economic and environmental aspects of such biofuel systems. As a suggestion, future studies need to be concentrated on investigating exergetic aspects of the unexplored pretreatment strategies as well as applying exergoeconomic and exergoenvironmental methods for providing information regarding the formation processes of cost and environmental burden.

Present work primarily deals with the exhaustive investigations of rapid de-lignification processes from source-sorted organic fractions that are recalcitrant in nature. Organic solid wastes (OSW) belongs to the organic fraction of municipal solid wastes (MSW) and they act as enormous potential substrate for alternative source of energy in the form of bio-fuels. Nevertheless, these substrates are not easily biodegradable and the degree of biodegradability is solely dependent on the composition & characteristic of organic solid wastes in municipal solid wastes. The component responsible for recalcitrance of organic solid wastes is lignin that occurs in variable amounts in different plant residues. In order to remove the recalcitrance from organic fraction municipal solid wastes and to make it more easily degradable by microbial consortia, certain pretreatment techniques have been adopted and they are applied either individually or in combined way for enhancement of bio-methanation i.e anaerobic digestion (AD) process. The goal of pretreatment method is to make the cellulose in micro-fibrils available for hydrolysis and improve the rate of hydrolysis. This paper reviews pretreatment techniques including physical, physico-chemical, chemical, biological methods respectively. The various effects of pretreatment on organic solid wastes are discussed separately and pretreatment methods have been compared on the basis of cost, efficiency and suitability to substrate.

Crop residues are exceptionally important as an alternative to raw materials for producing energy carriers, chemicals, and new materials in a post-petroleum scenario. Next-generation bioconversion processes in future biorefineries will make possible to convert biomass components into most of the products that are produced today from fossil feedstocks, as well as to not-yet-developed products that will become basic commodities for the future society. Crop residues are a realistic feedstock option for biorefineries considering their large availability, low cost, and renewable nature.
A basic process step in biorefineries is the pretreatment, which is directed to separate biomass resources into their main components and to activate cellulose towards enzymatic saccharification. Biomass constituents are then converted into different kinds of value-added products following a concept that is analogous to the way that today’s petroleum refineries produce fuels and products from petroleum.
Pretreatment research is today a hot issue, attracting attention not only from the academia, but also from the industrial sector, which looks forward to implementing the most promising methods in commercial-scale biorefineries. Pretreatment effectiveness is feedstock-dependent, and new research is required to develop efficient methods for different materials. This book covers some of the latest advances in research in developing efficient pretreatment methods and bioconversion approaches to be applied to crop residues of different nature.
The materials published in this book were written by experts in the pretreatment and bioconversion fields. I am confident that that reading the book will serve as a source of inspiration to scientists and entrepreneurs interested in making next-generation biorefineries of crop residues a commercial reality.

Biochemical conversion of lignocellulosic feedstocks to advanced biofuels and other commodities through a sugar-platform process involves a pretreatment step enhancing the susceptibility of the cellulose to enzymatic hydrolysis. A side effect of pretreatment is formation of lignocellulose-derived by-products that inhibit microbial and enzymatic biocatalysts. This review provides an overview of the formation of inhibitory by-products from lignocellulosic feedstocks as a consequence of using different pretreatment methods and feedstocks as well as an overview of different strategies used to alleviate problems with inhibitors. As technologies for biorefining of lignocellulose become mature and are transferred from laboratory environments to industrial contexts, the importance of management of inhibition problems is envisaged to increase as issues that become increasingly relevant will include the possibility to use recalcitrant feedstocks, obtaining high product yields and high productivity, minimizing the charges of enzymes and microorganisms, and using high solids loadings to obtain high product titres.

Biomass pretreatment for depolymerizing lignocellulosics to fermentable sugars has been studied for nearly 200 years. Researches have aimed at high sugar production with minimal degradation to inhibitory compounds. Chemical, physico-chemical and biochemical conversions are the most promising technologies. This article reviews the advances and current trends in the pretreatment of lignocellulosics for a prosperous biorefinery.

The objective of this work is to study the ageing state of a used reverse osmosis (RO) membrane taken in Algeria from the Benisaf Water Company seawater desalination unit. The study consists of an autopsy procedure used to perform a chain of analyses on a membrane sheet. Wear of the membrane is characterized by a degradation of its performance due to a significant increase in hydraulic permeability (25%) and pressure drop as well as a decrease in salt retention (10% to 30%). In most cases the effects of ageing are little or poorly known at the local level and global measurements such as (flux, transmembrane pressure, permeate flow, retention rate, etc.) do not allow characterization. Therefore, a used RO (reverse osmosis) membrane was selected at the site to perform the membrane autopsy tests. These tests make it possible to analyze and identify the cause as well as to understand the links between performance degradation observed at the macroscopic scale and at the scale at which ageing takes place. External and internal visual observations allow seeing the state of degradation. Microscopic analysis of the used membranes surface shows the importance of fouling. In addition, quantification and identification analyses determine a high fouling rate in the used membrane whose foulants is of inorganic and organic nature. Moreover, the analyses proved the presence of a biofilm composed of protein.

Plants have evolved their lignocellulosic cell walls through complex structural and chemical mechanisms to protect itself against microbial attacks, which makes native lignocellulosic biomass recalcitrant to enzymatic deconstruction. Pretreatment is a crucial step in the biological conversion of biomass as it can render structural changes in the plant cell wall to reduce the biomass recalcitrance, thus enhancing its sugar release performance. There have been many efforts to develop effective pretreatment technologies to overcome the biomass re-calcitrance with a primary focus on the efficient conversion of biomass carbohydrates to liquid fuels, while lignin is significantly underutilized despite its bulk amount and high-value opportunities. In this study, the effects of two recent organosolv pretreatment strategies, co-solvent enhanced lignocellulosic fractionation (CELF) and γ-Valerolactone (GVL) pretreatments, on physicochemical properties of poplar were investigated and compared with the effects of conventional ethanol organosolv pretreatment. Diverse physicochemical properties of biomass including chemical compositions, molecular weights of cellulose and lignin, aromatics and inter-unit linkages of lignin, lignin hydroxyl group contents, cellulose crystallinity, and accessible surface area of cellulose were analyzed before and after pretreatments. The results revealed how each organic solvent pretreatment system affected biomass structural characteristics and recalcitrance.

The current review is an attempt to cover various pre-treatment strategies such as physical, chemical,
organosolve and biological pre-treatment in order to change the crystallinity of lignocellulosic biomass
along with methods and strategies for inhibitor detoxification for improving the cellulose hydrolysis and
fermentation. The presence of lignin in lignocellulosic biomass is the biggest hurdle and therefore a judicial
pre-treatment selection technique is important, based on lignocellulosic mass composition analysis for
improving overall saccharification. The production of inhibitors during pre-treatment is another cause of low
saccharification owing to deactivation of cellulase enzyme. In this review a comprehensive discussion has
been made of the impact of various pre-treatment strategies on overall hydrolysis and saccharification in
view of the varied composition of lignocellulosic biomass. Various detoxification approaches have also been
discussed, along with the economical bioprocessing issue, and their advantages and disadvantages. Bio
refinery approaches have been important in this regard to make bioethanol production more economical

Pretreatment is commonly used to reduce recalcitrance of the lignin-carbohydrate matrix. In this study, leading pretreatment technologies, including dilute sulfuric acid, liquid hot water, alkaline, and organosolv pretreatments, were applied to the selected Populus trichocarpa genotype with relatively low lignin content to elucidate cellulose physicochemical property changes and digestibility-related factors. Pretreated Populus trichocarpa (BESC 131) exhibited higher accessibility and glucose yield than the untreated biomass. Chemical composition and Fourier transform infrared (FTIR) analysis results revealed that hemicellulose and lignin were removed to a varying extent depending on the pretreatment techniques applied. The degree of polymerization of the cellulose was decreased to the largest extent after dilute acid pretreatment, followed by organosolv, alkaline, and liquid hot water pretreatments. Cellulose crystallinity index was slightly changed after the pretreatments; however, its differences were not remarkable between those pretreatment techniques. Among four different pretreatments, organosolv was the most effective pretreatment technology in terms of sugar release, which was three times higher than that of the untreated native biomass. Among all of the tested cell wall traits, the lignin content of Populus trichocarpa was the most remarkable feature associated with glucose release, though Populus trichocarpa recalcitrance was not solely dependent on any single factor.

Heterogeneity and rigidity of lignocellulose causing resistance to its deconstruction have provided technical and economic challenges in the current biomass conversion processes. Lignin has been considered as a crucial re-calcitrance component in biomass utilization. An in-depth understanding of lignin properties and their influences on biomass conversion can provide clues to improve biomass utilization. Also, utilization of lignin can significantly increase the economic viability of biorefinery. Recent lignin-targeting pretreatments have aimed not only to overcome recalcitrance for biomass conversion but also to selectively fractionate lignin for lignin valorization. Numerous studies have been conducted in biomass characteristics and conversion technologies, and the role of lignin is critical for lignin valorization and biomass pretreatment development. This review provides a comprehensive review of lignin-related biomass characteristics, the impact of lignin on the biological conversion of biomass, and recent lignin-targeting pretreatment strategies. The desired lignin properties in biorefinery and future pretreatment directions are also discussed.

Organosolv pulping can be used as a pretreatment step in bioethanol production. In addition to ethanol, organosolv pulping allows for the production of a pure lignin product and other co-products. Based on publicly available information, conceptual process design and simulation model were developed for an organosolv process. The simulation model was used to calculate the mass and energy balances and approximate fossil-based carbon dioxide (CO 2) emissions for the process. With a hardwood feed of 2,350 dry metric tons (MT) per day, 459 MT/day (53.9 million gallons per year) of ethanol was produced. This corresponded to a carbohydrate to ethanol conversion of 64 %. The production rates of lignin, furfural, and acetic acid were 310, 6.6, and 30.3 MT/day, respectively. The energy balance indicated that the process was not energy self-sufficient. In addition to bark and organic residues combusted to produce energy, external fuel (natural gas) was needed to cover the steam demand. This was largely due to the energy consumed in recovering the solvent. Compared to a dilute acid bioethanol process, the organosolv process was estimated to consume 34 % more energy. Allocating all emissions from natural gas combustion to the produced ethanol led to fossil CO 2 emissions of 13.5 g per megajoule (MJ) of ethanol. The total fossil CO 2 emissions of the process, including also feedstock transportation and other less significant emission sources, would almost certainly not exceed the US Renewable Fuel Standard threshold limit (36.5 g CO 2 /MJ ethanol).

Hot-air (75 -100°C) pasteurisation (HAP) of birch-wood-based substrate was compared to conventional autoclaving (steam at 121 °C) with regard to shiitake growth and yield, chemical composition of heat-pretreated material and spent mushroom substrate (SMS), enzymatic digestibility of glucan in SMS, and theoretical bioethanol yield. Compared to autoclaving, HAP resulted in faster mycelial growth, earlier fructification, and higher or comparable fruit-body yield. The heat pretreatment methods did not differ regarding the fractions of carbohydrate and lignin in pretreated material and SMS, but HAP typically resulted in lower fractions of extractives. Shiitake cultivation, which reduced the mass fraction of lignin to less than half of the initial without having any major impact on the mass fraction of glucan, enhanced enzymatic hydrolysis of glucan about four-fold. The choice of heating method did not affect enzymatic digestibility. Thus, HAP could substitute autoclaving and facilitate combined shiitake mushroom and bioethanol production.

Conversion of lignocellulosic biomass to fuels and chemicals has attracted immense research and development around the world. Lowering recalcitrance of biomass in a cost-effective manner is a challenge to commercialize biomass-based technologies. Deep eutectic solvents (DESs) are new 'green' solvents that have a high potential for biomass processing because of their low cost, low toxicity, biodegradability, easy recycling and reuse. This article discusses the properties of DESs and recent advances in their application for lignocellulosic biomass processing. The effectiveness of DESs in hydrolyzing lignin-carbohydrate complexes, removing lignin/hemi-cellulose from biomass as well as their effect on biomass deconstruction, crystallinity and enzymatic digestibility have been discussed. Moreover, this review presents recent findings on the compatibility of natural DESs with enzymes and microorganisms.

This study aims to perform a regression analysis which leads to the optimization on the
operating conditions of ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate ([EMIM]oAc)
pretreatment on sugarcane bagasse (SCB). The structural changes on SCB during
pretreatment were also examined. The effects of temperature, time and solid loading on
reducing sugar (RS) yield obtained from enzymatic hydrolysis of pretreated SCB were
investigated by applying Central Composite Design (CCD) of Response Surface Methodology
(RSM). Results from CCD were modeled into a second order polynomial equation and
the model shows a good correlation between predicted and experimental values. The
optimized condition for [EMIM]oAc pretreatment were 145
C, 15 min and 14 wt% of solid
loading with an optimum RS yield of 69.7%. Characterization of SCB was carried out and
there were no significant difference between the chemical composition of untreated and
[EMIM]oAc-pretreated SCB. Pretreated SCB was found to be porous, less crystalline and
favorable to enzymatic hydrolysis as proven by Scanning Electron Microscopy (SEM), X-ray
Powder Diffraction (XRD) analysis and Fourier Transform Infrared (FTIR) analysis. In short,
[EMIM]oAc pretreatment shows good performance in improving the RS yield after
enzymatic hydrolysis besides giving desirable structural modification on pretreated SCB.
These are of great benefit to the subsequent downstream processes.

Despite the enormous potential shown by recent biorefineries, the current bioeconomy still encounters multifaceted challenges. To develop a sustainable biorefinery in the future, multidisciplinary research will be essential to tackle technical difficulties. Herein, we leveraged a known plant genetic engineering approach that results in aldehyde-rich lignin via down-regulation of cinnamyl alcohol dehydrogenase (CAD) and disruption of monolignol bio-synthesis. We also report on renewable deep eutectic solvents (DESs) synthesized from phenolic aldehydes that can be obtained from CAD mutant biomass. The transgenic Arabidopsis thaliana CAD mutant was pretreated with the DESs and showed a twofold increase in the yield of fermentable sugars compared with wild type (WT) upon enzymatic saccharification. Integrated use of low-recalcitrance engineered biomass, characterized by its aldehyde-type lignin subunits, in combination with a DES-based pretreat-ment, was found to be an effective approach for producing a high yield of sugars typically used for cellulosic biofuels and biobased chemicals. This study demonstrates that integration of renewable DES with plant genetic engineering is a promising strategy in developing a closed-loop process. green solvent | bioenergy | cinnamyl alcohol dehydrogenase | lignocellulosic biomass T he modern lignocellulosic biorefinery strives to develop new processes and products to achieve a sustainable energy future. Although renewable fuels from lignocellulosic biomass have proven to be alternatives to fossil fuels, innovative technologies are still required to build economically viable processes for converting biomass to fuels, chemicals, and materials (1). Recent efforts to overcome such barriers include (i) developing a feedstock-agnostic biomass pretreatment, (ii) engineering microorganisms that can catabolize both monosaccharides and lignin, and (iii) understanding biosynthesis of plant cell walls to develop engineered biomass with improved properties for biofuels and bioproducts. In lignocellulosic biomass-to-ethanol processes, researchers have endeavored to develop a biocompatible and scalable biomass pretreatment process, design new microbial strains that can convert both pentose and hexose with enhanced resistance to inhibitors, and engineer feedstocks to provide high yields of sugars and readily processable lignin. In contrast to first-generation ethanol, which has been studied in great depth and is considered to be mature, the production of cellulosic ethanol from lignocellulosic biomass still requires overcoming technical and economic hurdles. In particular, lignin represents one of the primary factors contributing to the re-calcitrance of biomass as its presence restricts enzymatic hy-drolysis by nonproductive binding enzymes (2). Although recent studies have unlocked lignin's potential for various applications (3), it is still one of the most challenging biopolymers to work with because of its inherent recalcitrant structural characteristics. In this regard, reducing the total amount of lignin in lignocel-lulosic biomass has been a widely adopted strategy to improve saccharification and the extractability of biomass components (4). In addition, there have been many recent efforts to alter lignin monomeric composition in plants to render lignin more amenable to extraction or chemical depolymerization. For example , by targeting the monolignol biosynthetic pathway (Fig. 1), genetic down-regulation of caffeic acid 3-O-methyltransferase (COMT) (5), hydroxycinnamoyl-CoA shikimate hydroxycinnamoyl transferase (HCT) (6), cinnamoyl-CoA reductase (CCR) (7), fer-ulate 5-hydroxylase (F5H) (8, 9), caffeoyl shikimate esterase (CSE) (10), and cinnamyl alcohol dehydrogenase (CAD) (11) alter lignin content and/or composition, thus reducing biomass recalcitrance and resulting in an enhancement of saccharification efficiency. Recently, introducing an exotic feruloyl-CoA monolignol transferase Significance Deep eutectic solvents (DESs) have gained increasing attention due to their application-friendly properties, including universal solvating capabilities and wide tunability. Additionally, ease of synthesis and broad availability from inexpensive chemical components could render DESs more versatile solvents for biomass pretreatment, as compared with traditional ionic liquids. Because the long-term success of the biorefinery depends on the development of sustainable processes to convert lig-nocellulosics into biofuels, DESs derived from renewable sources such as lignin are highly desirable. We herein present our innovative process that integrates the use of low-recalcitrant engineered biomass with its pretreatment using lignin-derived DESs. The promising results described by near-theoretical sugar yield demonstrate the effectiveness of the integrated process, opening up opportunities toward a sustainable and circular bioeconomy.

Microalgae species including Chlamydomonas mexicana, Micractinium reisseri, Scenedesmus obliquus and Tribonema aequale were cultivated in batch cultures, and their biochemical composition was determined. C. mexicana showed the highest carbohydrate content of 52.6 % and was selected for further study. Sonication pretreatment under optimum conditions (at 40 kHz, 2.2 Kw, 50 °C for 15 min) released 74 ± 2.7 mg g−1 of total reducing sugars (TRS) of dry cell weight, while the combined sonication and enzymatic hydrolysis treatment enhanced the TRS yield by fourfold (280.5 ± 4.9 mg g−1). The optimal ratio of enzyme [E]:substrate [S] for maximum TRS yield was [1]:[5] at 50 °C and pH 5. Combined sonication and hydrolysis treatment released 7.3 % (27.1 ± 0.9 mg g−1) soluble protein of dry cell weight, and further fermentation of the dissolved carbohydrate fraction enhanced the soluble protein content up to 56 % (228.4 mg g−1) of total protein content. Scanning and transmission electron microscopic analyses indicated that microalgae cells were significantly disrupted by the combined sonication and enzyme hydrolysis treatment. This study indicates that pretreatment and subsequent fermentation of the microalgal biomass enhance the recovery of carbohydrates and proteins which can be used as feedstocks for generation of biofuels.

This study aimed to develop an energy-and resource-efficient process for the coproduction of edible mushroom, fermentable sugar and solid biofuel from wood residues. A promising potential was revealed for wood ear fungus (Auricularia auricular-judae), which yielded about 200 g mushroom per kg dry birch-based substrate, with concomitant degradation of 76.8 and 85.7% of lignin and xylan, respectively, in the substrate. Substrate pasteurisation by hot-air (85e100 C) was as effective as by energy intensive autoclaving (121 C), resulting comparable mushroom growth and degradation of lignocellulose. The spent mushroom substrate (SMS) contained 28e33% glucan, which upon analytical enzymatic sacchar-ification released around 46% of the potentially-achievable glucose, corresponding to a 2.3efold enzy-matic digestibility compared with that of the raw substrate. The solid leftover generated after enzymatic hydrolysis revealed high thermal energy value and promising combustion characteristics, showing a plausibility to be recycled as solid fuel for self-supporting energy system and space heating.

Biological valorization of biomass most often depends on the efficient reduction of plant cell wall recalcitrance and conversion of lignin-the most recalcitrant constituent-to fuels, chemicals and/or value-added substances. Lignin conversion to fuels and value-added chemicals requires a sound understanding of the structure of lignin before and after different pretreatments. In the current work, an effort has been made to compare the structural differences in isolated pine lignin after one-(alkaline) and two-step (alkaline/dilute acid and alkaline/steam explosion) pretreatments. Our results indicate removal of the low molecular weight fraction of lignin after an initial alkaline pretreatment. A subsequent dilute acid pretreatment resulted in the loss of lignin inter-unit linkages such as β-O-4' aryl ethers. However, with a steam explosion pretreatment, lignin exhibited a competing condensation process leading to increased condensed lignin structures.

A sodium chlorite bath for scouring and bleaching of linen fabric by a one-step process is activated by glyoxal as an organic-reducing compound having two aldehyde functional groups. Such activator has been found to be effective in bringing about the progressive decomposition of sodium chlorite. The treatment was achieved under a variety of conditions, and the bleaching effect of sodium chlorite/glyoxal system was appraised by monitoring the treated samples for the degree of whiteness (WI), loss in fabric weight (LW), wettability (W), carbonyl (CO) content, carboxyl (COOH) content, percentage of sodium chlorite decomposed, and tensile strength (TS). The best conditions for concurrent desizing, scouring, and bleaching of linen fabric with excellent whiteness index and acceptable tenacity were found to be 60°C and at initial pH of 10.35, with aqueous solution containing 5g/L NaClO2 , glyoxal 6 mmol/L, and 2g/L wetting agent for 120 min using the material-to‐liquor ratio (M/L) 1:30. Tentative mechanisms were also reported to account for the bleaching action of NaClO2  /glyoxal system.

Banana agricultural waste is one of the potential lignocellulosic substrates which are mostly un-utilized
but sufficiently available in many parts of the world. In the present study, suitability of banana waste for
biofuel production with respect to pretreatment and reducing sugar yield was assessed. The effectiveness
of both acid and alkali pretreatments along with autoclaving, microwave heating and ultrasonication on
different morphological parts of banana (BMPs) was studied. The data were statistically analyzed using
ANOVA and numerical point prediction tool of MINITAB RELEASE 14. Accordingly, the optimum cumulative
conditions for maximum recovery of reducing sugar through acid pretreatment are: leaf (LF) as the
substrate with 25 min of reaction time and 180 C of reaction temperature using microwave. Whereas,
the optimum conditions for alkaline pretreatments are: pith (PH) as the substrate with 51 min of reaction
time and 50 C of reaction temperature using ultrasonication (US).

With rapidly increased interests in biomass, diverse chemical and biological processes have been applied for biomass utilization. Fourier transform infrared (FTIR) analysis has been used for characterizing different types of biomass and their products, including natural and processed biomass. During biomass treatments, some solvents and/or catalysts can be retained and contaminate biomass. In addition, contaminants can be generated by the decomposition of biomass components. Herein, we report FTIR analyses of a series of contaminants, such as various solvents, chemicals, enzymes, and possibly formed degradation by-products in the biomass conversion process along with poplar biomass. This information helps to prevent misunderstanding the FTIR analysis results of the processed biomass.