Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae

One pot synthesis of furan-modified lignin from agricultural waste via lignin-first approach

This study investigated a lignin-first approach to produce furan-modified lignin from sugarcane bagasse (SB), rice hull (RH), and sunn hemp biomass (SHB) using 5 methylfurfural (MF) and 5 methul-2-furanmethanol (MFM). The reaction time (5 h) was selected based on the delignification of SB using methanol and Ru/C catalyst which yielded the highest hydroxyl content. Delignification of SB with various MF weight ratios (1:1, 1:2, 1:3, 2:1, and 3:1) revealed that 1:1 and 2:1 ratios produced the highest hydroxyl content (7.7 mmol/g) and bio-oil yield (23.2 % wt% total weight). Further exploration identified that RH and MF at 1:1 ratio and SHB and MF at a 2:1 ratio produced the highest hydroxyl content (13.0 mmol/g) and bio-oil yield (31.6 % wt% tot. weight). This study developed a one-step method to extract and modify lignin with furan compounds simultaneously while opening new avenues for developing value-added products.

Adsorption and aggregation of Cu2+ on carboxymethylated sugarcane bagasse: Adsorption behavior and mechanism

Abundant biomass resources provide us with sufficient material basis, while a large amount of bio-waste is also produced and the high-value utilization of bio-waste is still highly desirable. Herein, we reported a facile one-pot fabrication approach towards efficient utilization of sugarcane bagasse via carboxymethylation to adsorb and recycle Cu2+ ions. The modified sugarcane bagasse possessed outstanding adsorption efficiency, with a maximum capacity of 263.7 mg g-1, owing to the functional groups such as carboxyl and hydroxyl groups, as well as aromatic structure. It was noted that the carboxymethylated sugarcane bagasse (MSB40) swelled rapidly when suffering Cu2+ ions solution, and more adsorption sites were available since the physical diffusion barrier was removed, thereby enhancing the absorption capacity. Interestingly, Cu2+ ions could induce the aggregation of MSB40 due to the Cu2+ ions compress colloid double layer, neutralizes surface charges, which benefited the following separation process. Ultimately, copper oxide was recovered and the purity reached 97.9%. Additionally, in the presence of both Ca2+ and Mg2+ ions, MSB40 exhibited excellent selectivity for the adsorption of Cu2+ ions. This strategy offers a facile and novel clue for the high-value utilization of bio-waste and the recovery of copper for biomaterial and environmental applications.

Toward a zero waste approach: Utilization of sugarcane bagasse for dye removal and multienzymes production

Global production of sugarcane bagasse (SB) by sugar industries exceeds more than 100 tons per annum. SB is rich in lignin and polysaccharide and hence can serve as a low-cost energy and carbon source for the growth of industrially important microorganism. However, various other applications of SB have also been investigated. In this study, SB was used as an adsorbent to remove an azo dye, malachite green. Subsequently, the dye-adsorbed SB was fermented by Trametes pubescens MB 89 for the production of laccase enzyme. The fungal pretreated SB was further utilized as a substrate for the simultaneous production of multiple plant cell wall degrading enzymes including, cellulase, xylanase, pectinase, and amylase by thermophilic bacterial strains. Results showed that 0.1% SB removed 97.04% malachite green at 30°C after 30 min from a solution containing 66 ppm of the dye. Fermentation of the dye-adsorbed SB by T. pubescens MB 89 yielded 667.203 IU mL-1 laccase. Moreover, Brevibacillus borstelensis UE10 produced 38.41 and 18.6 IU mL-1 β-glucosidase and pectinase, respectively, by using fungal-pretreated SB. Cultivation of B. borstelensis UE27 in the medium containing the same substrate yielded 32.14 IU mL-1 of endoglucanase and 27.23 IU mL-1 of β-glucosidase. Likewise, Neobacillus sedimentimangrovi UE25 could produce a mix of β-glucosidase (37.24 IU mL-1 ), xylanase (18.65 IU mL-1 ) and endoglucanase (26.65 IU mL-1 ). Hence, this study led to the development of a method through which dye-containing textile effluent can be treated by SB along with the production of industrially important enzymes.

High-pressure microwave-assisted pretreatment of softwood, hardwood and non-wood biomass using different solvents in the production of cellulosic ethanol

BACKGROUND

Pretreatment is an indispensable stage of the preparation of lignocellulosic biomass with key significance for the effectiveness of hydrolysis and the efficiency of the production of cellulosic ethanol. A significant increase in the susceptibility of the raw material to further degradation can be attained as a result of effective delignification in high-pressure conditions. With this in mind, a method of high-pressure pretreatment using microwave radiation and various solvents (water, 40% w/v NaCS, 1% v/v H₂SO₄, 1% w/v NaOH or 60% v/v EtOH with an addition of 1% v/v H₂SO₄) was developed, enabling the acquisition of biomass with an increased susceptibility to the process of enzymatic hydrolysis. The medium obtained in this way can be used for the production of cellulosic ethanol via high-gravity technology (lignocellulosic media containing from 15 to 20% dry weight of biomass). For every type of biomass (pine chips, beech chips and wheat straw), a solvent was selected to be used during the pretreatment, guaranteeing the acquisition of a medium highly susceptible to the process of enzymatic hydrolysis.

RESULTS

The highest efficiency of the hydrolysis of biomass, amounting to 71.14 ± 0.97% (glucose concentration 109.26 ± 3.49 g/L) was achieved for wheat straw subjected to microwave-assisted pretreatment using 40% w/v NaCS. Fermentation of this medium produced ethanol concentration at the level of 53.84 ± 1.25 g/L. A slightly lower effectiveness of enzymatic hydrolysis (62.21 ± 0.62%) was achieved after high-pressure microwave-assisted pretreatment of beech chips using 1% w/v NaOH. The hydrolysate contained glucose in the concentration of 91.78 ± 1.91 g/L, and the acquired concentration of ethanol after fermentation amounted to 49.07 ± 2.06 g/L. In the case of pine chips, the most effective delignification was achieved using 60% v/v EtOH with the addition of 1% v/v H₂SO₄, but after enzymatic hydrolysis, the concentration of glucose in hydrolysate was lower than in the other raw materials and amounted to 39.15 ± 1.62 g/L (the concentration of ethanol after fermentation was ca. 19.67 ± 0.98 g/L). The presence of xylose and galactose was also determined in the obtained fermentation media. The highest initial concentration of these carbohydrates (21.39 ± 1.44 g/L) was observed in beech chips media after microwave-assisted pretreatment using NaOH. The use of wheat straw after pretreatment using EtOH with an addition of 1% v/v H₂SO₄ for the preparation of fermentation medium, results in the generation of the initial concentration of galactose and xylose at the level of 19.03 ± 0.38 g/L.

CONCLUSION

The achieved results indicate a high effectiveness of the enzymatic hydrolysis of the biomass subjected to high-pressure microwave-assisted pretreatment. The final effect depends on the combined use of correctly selected solvents for the different sources of lignocellulosic biomass. On the basis of the achieved results, we can say that the presented method indicates a very high potential in the area of its use for the production of cellulosic ethanol involving high-gravity technology.

Role of metagenomics in prospecting novel endoglucanases, accentuating functional metagenomics approach in second-generation biofuel production: a review

As the fossil fuel reserves are depleting rapidly, there is a need for alternate fuels to meet the day to day mounting energy demands. As fossil fuel started depleting, a quest for alternate forms of fuel was initiated and biofuel is one of its promising outcomes. First-generation biofuels are made from edible sources like vegetable oils, starch, and sugars. Second-generation biofuels (SGB) are derived from lignocellulosic crops and the third-generation involves algae for biofuel production. Technical challenges in the production of SGB are hampering its commercialization. Advanced molecular technologies like metagenomics can help in the discovery of novel lignocellulosic biomass-degrading enzymes for commercialization and industrial production of SGB. This review discusses the metagenomic outcomes to enlighten the importance of unexplored habitats for novel cellulolytic gene mining. It also emphasizes the potential of different metagenomic approaches to explore the uncultivable cellulose-degrading microbiome as well as cellulolytic enzymes associated with them. This review also includes effective pre-treatment technology and consolidated bioprocessing for efficient biofuel production.

Using liquefied biomass hydrogel to mitigate salinity in salt-affected soils

Salinity affects over 33% of irrigated farmland globally. Developing a low-cost, safe, and effective material as a soil salinity mitigation option would be of significant importance. This study proposed to synthesize a hydrogel using liquefied biomass from sugarcane bagasse, polyvinyl alcohol, and sodium tetraborate decahydrate. The effectiveness of the produced hydrogel in mitigating soil salinity was evaluated based on an incubation experiment at two salinity levels (5 and 10 dS m^-1). The experiment was conducted by mixing liquefied hydrogel with soil at four application rates (0, 1, 2, and 3% w/w) with three replications. Porewater and soil samples were tested for pH and electrical conductivity (EC). Soil samples were also analyzed for selected cations and anions. The results demonstrated that hydrogel significantly reduced porewater EC at both 5 and 10 dS m^-1 salt solutions. In addition, hydrogel reduced Cl^-, P, Ca²⁺, and Al³⁺ concentrations in soil samples with maximum reductions observed from 3% hydrogel treatment. However, pH of porewater showed a consistent increase with hydrogel application. The application of hydrogel also increased NH₄-N at high salt level. Overall, hydrogel has shown promising results in reducing soil salinity and could potentially be used as a soil amendment for saline soils.

Sustainable valorization of sugarcane residues: Efficient deconstruction strategies for fuels and chemicals production

The global climate crisis and the ongoing increase in fossil-based fuels have led to an alternative solution of using biomass for fuel production. Sugarcane bagasse (SCB) is an agricultural residue with a global production of more than 100 million metric tons and it has various applications in a biorefinery concept. This review brings forth the composition, life cycle assessment, and various pretreatments for the deconstruction techniques of SCB for the production of valuable products. The ongoing research in the production of biofuels, biogas, and electricity utilizing the bagasse was elucidated. SCB is used in the production of carboxymethyl cellulose, pigment, lactic acid, levulinic acid, and xylooligosaccharides and it has prospective in meeting the demand for global energy and environmental sustainability.

Prospects of soil microbiome application for lignocellulosic biomass degradation: An overview

Sustainable and practically viable biofuels production technology using lignocellulosic biomass is still seeking its way of implementation owing to some major issues involved therein. Unavailability of efficient microbial sources for the degradation of cellulosic biomass is one of the major roadblocks in biomass to biofuels production technology. In this context, utilization of microbiomes to degrade lignocellulaosic biomass is emerging as a rapid and effective approach that can fulfill the requirements of biomass based biofuels production technology. Therefore, the present review is targeted to explore soil metagenomic approach to improve the lignocellulosic biomass degradation processing for the cost-effective and eco-friendly application. Soil microbiomes consist of rich microbial community along with high probability of cellulolytic microbes, and can be identified by culture independent metagenomics method which can be structurally and functionally explored via genomic library. Therefore, in depth analysis and discussion have also been made via structural & functional metagenomics tools along with their contribution to genomic library. Additionally, the present review highlights currently existing bottlenecks along with their feasible solutions. This review will help to understand the basic research as well as industrial concept for the process improvement based on soil microbiome mediated lignocellulosic biomass degradation, and this may likely to implement for the low-cost commercial biofuels production technology.

Fabrication and Characterization of Effective Biochar Biosorbent Derived from Agricultural Waste to Remove Cationic Dyes from Wastewater

The main aim of this work is to treat sugarcane bagasse agricultural waste and prepare an efficient, promising, and eco-friendly adsorbent material. Biochar is an example of such a material, and it is an extremely versatile and eco-friendly biosorbent to treat wastewater. Crystal violet (CV)-dye and methylene blue (MB)-dye species are examples of serious organic pollutants. Herein, biochar was prepared firstly from sugarcane bagasse (SCB), and then a biochar biosorbent was synthesized through pyrolysis and surface activation with NaOH. SEM, TEM, FTIR, Raman, surface area, XRD, and EDX were used to characterize the investigated materials. The reuse of such waste materials is considered eco-friendly in nature. After that, the adsorption of MB and CV-species from synthetically prepared wastewater using treated biochar was investigated under various conditions. To demonstrate the study’s effectiveness, it was attempted to achieve optimum effectiveness at an optimum level by working with time, adsorbent dose, dye concentration, NaCl, pH, and temperature. The number of adsorbed dyes reduced as the dye concentrations increased and marginally decreased with NaCl but increased with the adsorbent dosage, pH, and temperature of the solution increased. Furthermore, it climbed for around 15 min before reaching equilibrium, indicating that all pores were almost full. Under the optimum condition, the removal perecentages of both MB and CV-dyes were ≥98%. The obtained equilibrium data was represented by Langmuir and Freundlich isotherm models. Additionally, the thermodynamic parameters were examined at various temperatures. The results illustrated that the Langmuir isotherm was utilized to explain the experimental adsorption processes with maximum adsorption capacities of MB and CV-dyes were 114.42 and 99.50 mgg⁻¹, respectively. The kinetic data were estimated by pseudo-first and pseudo-second-order equations. The best correlation coefficients of the investigated adsorption processes were described by the pseudo-second-order kinetic model. Finally, the data obtained were compared with some works published during the last four years.

Comprehensive approach of methods for microstructural analysis and analytical tools in lignocellulosic biomass assessment - A review

The trend in the modern world is to replace fossil fuels with green energy sources in order to reduce their environmental impact. The biorefinery industry, within this premise, needs to establish quantitative and qualitative analytical methods to better understand lignocellulosic biomass composition and structure. This paper presents chemical techniques (chromatography, thermal analysis, HRMS, FTIR, NIR, and NMR) and physicochemical techniques (XRD, optical and electron microscopy techniques - Confocal fluorescence, Raman, SPM, AFM, SEM, and TEM) for the microstructural characterization of lignocellulosic biomass and its derivatives. Each of these tools provides different and complementary information regarding molecular and microstructural composition of lignocellulosic biomass. Understanding these properties is essential for the design and operation of associated biomass conversion processing facilities. PAT, monitored in real-time, ensures an economical and balanced mass-energy process. This review aimed to help researchers select the most suitable analytical technique with which to investigate biomass feedstocks with recalcitrant natures.

Effects of Microwave-Assisted Liquid Hot Water Pretreatment on Chemical Composition and Structure of Moso Bamboo

The effects of microwave assisted liquid hot water (MA-LHW) pretreatment on the chemical composition of Moso bamboo were investigated, and the fiber structure of pretreated residues were studied. The results showed that MA-LHW pretreatment had high selectivity for the degradation of hemicellulose in Moso bamboo, and the extracted hemicellulose could be used to prepare xylooligosaccharide through enzyme depolymerization. The degradation rates of cellulose and lignin after MA-LHW pretreatment were only 14.73% and 7.18%, which were significantly lower than those of LHW pretreatment; 155.0 mg/g xylobiose and 61.0 mg/g xylotrisoe can be obtained after enzymatic hydrolysis, and the yield of xylo-oligosaccharide reached 80.59% of the theoretical conversion rate. MA-LHW pretreatment increased the removal of hemicellulose, lignin, and other non-crystalline parts in bamboo materials, and more cellulose with crystalline structure was retained, which increased the CrI value of Moso bamboo by 14.84%. FTIR spectra showed that the characteristic peak intensity of hemicellulose was significantly reduced after MA-LHW pretreatment, which confirmed the selective degradation of hemicellulose by MA-LAW pretreatment. Moreover, MA-LHW pretreatment also destroyed O-H, C-H, C-O-C, and β-glucoside bonds in Moso bamboo fiber, caused by the recombination and synthesis of some groups (-CH2 and C=O) of cellulose, hemicellulose, and lignin destroyed under pretreatment conditions.

Screening of Cucumber Fusarium Wilt Bio-Inhibitor: High Sporulation Trichoderma harzianum Mutant Cultured on Moso Bamboo Medium

Cucumber fusarium wilt is a soil-borne disease which causes serious production decrease in cucumber cultivation world widely. Extensive using of chemical pesticides has caused serious environmental pollution and economic losses, therefore, it is particularly urgent to develop efficient, safe and pollution-free biopesticide. In this study, a mutant strain of Trichoderma harzianum cultivated in moso bamboo medium was proved to be an efficient bio-inhibitor of the disease. The mutant strain T. harzianum T334, was obtained by three microwave mutagenesis cycles with an irradiation power of 600 W and irradiation time of 40 s. In contrast to the original strain, the inhibition rate on cucumber fusarium wilt of the strain T334 increased from 63 to 78%. In this work, disk milling pretreatment of moso bamboo has shown significant beneficial effects on both biotransformation and sporulation of T334. Its sporulation reached 3.7 × 10⁹ cfu/g in mushroom bags with 90% bamboo stem powder (pretreated by disk milli), 9.5% bamboo leaf powder and 0.5% wheat bran when the ratio of solid to liquid was 4:6, the inoculum amount was 10%, and the culture temperature was 28°C. These results provide an alternative bioinhibitor for the control of cucumber fusarium wilt, and a potential usage of moso bamboo in the production of microbial pesticide.

Wild Halophytic Phragmites karka Biomass Saccharification by Bacterial Enzyme Cocktail

Biofuel derived from halophytic biomass is getting attention owing to the concerns of energy versus food crisis. The disadvantages associated with edible bioenergy resources necessitate the need to explore new feedstocks for sustainable biofuel production. In this study, biomass from locally available abundant halophytes (Panicum antidotale, Phragmites karka, Halopyrum mucronatum, and Desmostachya bipinnata) was screened for saccharification by an enzyme cocktail composed of cellulase, xylanase, and pectinase from Brevibacillus borstelensis UE10 and UE27, Bacillus aestuarii UE25, Aneurinibacillus thermoaerophilus UE1, and Bacillus vallismortis MH 1. Two types of pretreatment, i.e., with dilute acid and freeze-thaw, were independently applied to the halophytic biomass. Saccharification of acid-pretreated P. karka biomass yielded maximum reducing sugars (9 mg g^-1) as compared to other plants. Thus, the factors (temperature, pH, substrate concentration, and enzyme units) affecting its saccharification were optimized using central composite design. This statistical model predicted 49.8 mg g^-1 of reducing sugars that was comparable to the experimental value (40 mg g^-1). Scanning electron microscopy and Fourier-transform infrared spectroscopy showed significant structural changes after pretreatment and saccharification. Therefore, halophytes growing in saline, arid, and semi-arid regions can be promising alternative sources for bioenergy production.

Isolation and Screening of Microorganisms for the Effective Pretreatment of Lignocellulosic Agricultural Wastes

Lignocellulosic waste is the most abundant biorenewable biomass on earth, and its hydrolysis releases highly valued reducing sugars. However, the presence of lignin in the biopolymeric structure makes it highly resistant to solubilization thereby hindering the hydrolysis of cellulose and hemicellulose. Microorganisms are known for their potential complex enzymes that play a dominant role in lignocellulose conversion. Therefore, the current study was designed to isolate and screen potential microorganisms for their selective delignification ability for the pretreatment of lignocellulosic biomass. An extensive isolation and screening procedure yielded 36 desired isolates (22 bacteria, 7 basidiomycete fungi, and 7 filamentous fungi). Submerged cultivation of these desired microorganisms revealed 4 bacteria and 10 fungi with potent lignocellulolytic enzyme activities. The potent isolates were identified as Pleurotus, Trichoderma, Talaromyces, Bacillus, and Chryseobacterium spp. confirmed by morphological and molecular identification. The efficiency of these strains was determined through enzyme activities, and the degraded substrates were analyzed through scanning electron microscopy (SEM) and X-ray diffraction (XRD). Among all isolated microbes, Pleurotus spp. were found to have high laccase activity. The cellulose-decomposing and selective delignification strains were subjected to solid-state fermentation (SSF). SSF of field waste corn stalks as a single-carbon source provides Pleurotus spp. better condition for the secretion of ligninolytic enzymes. These isolated ligninolytic enzymes producing microorganisms may be used for the effective pretreatment of lignocellulosic agricultural wastes for the production of high value-added natural products by fermentation.

Removal of hazardous dye from aqueous media using low-cost peanut (Arachis hypogaea) shells as adsorbents

In the present article, an attempt is made for simple, low-cost, and efficient removal of Auramine dye using peanut (Arachis hypogaea) shells as adsorbents. Two different forms of adsorbents distilled water washed peanut shells (DPS) and NaOH treated peanut shells (NPS) were used as adsorbents. Both the adsorbents were studied using BET, pH_PZC , FTIR, SEM, TGA, and XRD characterization techniques. Adsorption parameters such as effect of contact time, pH, initial dye concentration, adsorbent dose, and temperature were also assessed. Isotherm analysis at optimum conditions showed Langmuir fitted better with a q_m value of 96.15 mg/g for DPS and 294.12 mg/g for NPS; while in kinetic analysis, pseudo-second order was superior. Thermodynamics study stated that adsorption process was endothermic in nature. Overall outcomes establish that the two forms of peanut shells, DPS, and NPS were excellent in removal of Auramine dye and are low cost also as preparation cost of DPS and NPS is 68.73 INR and 106.19 INR per kg, respectively. PRACTITIONER POINTS: Removal of Auramine dye from aqueous media using different forms of peanut (Arachis hypogaea) shells as adsorbents is discussed. q_m (Langmuir) using DPS and NPS were found to be 96.15 and 294.12 mg/g, respectively. Preparation cost of DPS was 68.73 INR per 1 kg, whereas for NPS it was 106.19 INR per 1 kg.

Upgrading from batch to continuous flow process for the pyrolysis of sugarcane bagasse: Structural characterization of the biochars produced

The waste from agriculture can be used for biochar production by the pyrolysis process. The present work aimed was to produce sugarcane bagasse biochars using different temperatures and processes (batch and pilot-scale continuous flow). The samples were characterized by FTIR, functional group pKa, elemental analysis, zeta potential, Raman spectroscopy, EPR, and SEM. The FTIR spectra showed bands around 1400-1650 cm^-1 corresponded to vibrations of CC bonds and pKa revealed the presence of carboxylic acids (pKa ≤5) and lactones (pKa ~5-9). The elemental analyses (H/C ~ 0.31) and Raman spectra (I_D/I_G ~ 0.55) confirmed greater carbonization and less structural disorder of the material produced using the continuous flow process. SEM images showed that the biochar morphologies were similar to that of the precursor biomass, with the formation of pores. The continuous flow process is a promising technique for the production of biochars with high carbon contents and aromatic structures, as well as lower defect degrees, compared to biochars produced using a batch process.

Supporting role of lignin in immobilization of yeast on sugarcane bagasse for continuous pectinase production

BACKGROUND

Lignocellulosic wastes are pretreated prior to their utilization in fermentation processes. Such pretreatment also alters the topological features of the substrates, and therefore the suitability of pretreated waste as immobilization matrix for microbial cells needs investigation.

RESULTS

In this study, the effect of chemical pretreatment of sugarcane bagasse (SB) for its subsequent utilization as a matrix to immobilize a pectinolytic yeast, Geotrichum candidum AA15, was evaluated using cell retention, concentration of immobilized cells, immobilization efficiency, scanning electron microscopy and Fourier transform infrared spectroscopy of the substrate and pectinase titers obtained after recycling. The results revealed that untreated SB is more efficient for immobilization with higher values of cell retention and pectinase productivity (99.78%) retained for up to six production cycles. It was deduced that removal of lignin by pretreatment negatively influenced the ability of SB to support cell adhesion, as lignin acts as a sealing agent that provides strength to the substrate.

CONCLUSIONS

The strategy of utilizing SB as immobilization matrix was found effective at the laboratory scale as it improved pectinase production and may be investigated further for large-scale and cost-effective production. © 2020 Society of Chemical Industry.

Combined pretreatment of sugarcane bagasse using alkali and ionic liquid to increase hemicellulose content and xylanase production

BACKGROUND

Lignin in sugarcane bagasse (SB) hinders its utilization by microorganism, therefore, pretreatment methods are employed to make fermentable components accessible to the microbes. Multivariate analysis of different chemical pretreatment methods can aid to select the most appropriate strategy to valorize a particular biomass.

RESULTS

Amongst methods tested, the pretreatment by using sodium hydroxide in combination with methyltrioctylammonium chloride, an ionic liquid, (NaOH+IL) was the most significant for xylanase production by Bacillus aestuarii UE25. Investigation of optimal levels of five significant variables by adopting Box-Behnken design (BBD) predicted 20 IU mL^- 1 of xylanase and experimentally, a titer of 17.77 IU mL^- 1 was obtained which indicated the validity of the model. The production kinetics showed that volumetric productivity of xylanase was much higher after 24 h (833.33 IU L^- 1 h^- 1) than after 48 h (567.08 IU L^- 1 h^- 1). The extracted xylan from SB induced more xylanase in the fermentation medium than pretreated SB or commercially purified xylan. Nuclear Magnetic Resonance, Fourier transform infrared spectroscopy and scanning electron microscopy of SB indicated removal of lignin and changes in the structure of SB after NaOH+IL pretreatment and fermentation.

CONCLUSION

Combined pretreatment of SB with alkali and methyltrioctylammonium chloride appeared better than other chemical methods for bacterial xylanase production and for the extraction of xylan form SB.

Pretreatment of Cellulose from Sugarcane Bagasse with Xylanase for Improving Dyeability with Natural Dyes

In this study, cellulose was obtained from sugarcane bagasse (SCB) and treated with xylanase to remove residual noncellulosic polymers (hemicellulose and lignin) to improve its dyeability. The cellulose fibers were dyed with natural dye solutions extracted from the heart wood of Ceasalpinia sappan Linn. and Artocarpus heterophyllus Lam. Fourier-transform infrared (FTIR) spectroscopy, Raman analysis, and whiteness index (WI) indicated successful extraction of cellulose by eliminating hemicellulose and lignin. The FTIR analysis of the dyed fibers confirmed successful interaction between natural dyes and cellulose fibers. The absorption (K) and scattering (S) coefficient (K/S) values of the dyed fibers increased in cellulose treated with xylanase before dyeing. Scanning electron microscopy (SEM) analysis showed that the surface of alkaline-bleached fibers (AB-fibers) was smoother than alkaline-bleached xylanase fibers (ABX-fibers), and the presence of dye particles on the surface of dyed fibers was confirmed by energy-dispersive spectrometry (EDS) analysis. The X-ray diffraction (XRD) revealed a higher crystallinity index (CrI), and thermal gravimetric analysis (TGA) also presented higher thermal stability in the dyed fibers with good colorfastness to light. Therefore, xylanase treatment and natural dyes can enhance dyeability and improve the properties of cellulose for various industrial applications.

Weak-base pretreatment to increase biomethane production from wheat straw

Weak-base pretreatment of wheat straw was investigated for its ability to improve biomethane production. Anaerobic digestion (AD) was performed on wheat straw pretreated with 3%, 5%, or 7% Na₂CO₃ as a weak base. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated disruption of lignocellulosic structures by pretreatment. In the 5% Na₂CO₃ treatment group, cellulose and hemicellulose were retained effectively, with efficient removal of lignin. The removal rates of cellulose, hemicellulose, and lignin were 27.9%, 20.4%, and 31.0%, respectively, after 5% Na₂CO₃ pretreatment. The methane content (53.3-77.3%) was improved in the 5% Na₂CO₃ treatment group, with maximum methane production (307.9 L/kg VS) that was 41.6% higher than that of the untreated sample. Cellulose and hemicelluloses were degraded 59.3% and 56.3% after AD. It took 20 days to reach 80% of the maximum cumulative methane production for the 5% Na₂CO₃ pretreatment group, which was 4 days faster than the untreated group. These results indicate that 5% Na₂CO₃ pretreatment improve the lignocellulose structure of wheat straw, allowing better biodegradability of wheat straw in AD for increased biogas production, enhanced methane content, and decreased digestion time.

Development of One Pot Strategy for Hyper Production and In Vivo Evaluation of Lovastatin

The aim of this project was to improve the Aspergillus terreus strain and pretreatment of sugarcane bagasse as carrier substrate for bulk production of lovastatin, a cholesterol-lowering drug, in solid state fermentation. Sugarcane bagasse was treated with alkali (1–3% NaOH) for the conversion of complex polysaccharides into simple sugars for better utilization of carrier substrate by microorganism for maximum lovastatin production. Ethidium bromide (time of exposure 30–180 min) was used to induce mutation in Aspergillus terreus and the best mutant was selected on the basis of inhibition zone appeared on petri plates. Fermented lovastatin was quantified by high-performance liquid chromatography. The fermented lovastatin, produced by parent and mutant Aspergillus terreus strain, was checked on body weight, blood glucose and serum cholesterol, ALT, AST, HDL-C, LDL-C, TG and TC levels of rats for their cholesterol lowering capacity. Our results indicate that selected strain along with 2% NaOH treated sugar cane bagasse was best suitable for bulk production of lovastatin by fermentation and fermented lovastatin effectively lower the cholesterol level of rats.

Evaluation of Factors Affecting Saccharification of Sugarcane Bagasse Using Cellulase Preparation from a Thermophilic Strain of Brevibacillus sp

This study focuses on the production of cellulase from a thermophilic bacterium Brevibacillus sp. MT5 and prospects of utilizing the enzyme preparation for the saccharification of sugarcane bagasse (SB). The data revealed that cellulase produced at 70 °C expressed an IFPU (international filter paper unit) of 1.776 when assayed at 60 °C and showed good activity towards SB. Consequently, the conditions affecting saccharification of SB were studied by employing a Plackett-Burman design and reducing sugars were determined by dinitrosalicylic acid method and glucose oxidase kit. The analysis of the design highlighted that the factors affecting the hydrolysis process varies in terms of their significance with respect to the duration of the reaction, however, agitation remained a consistent significant factor throughout the process. Gravimetric analysis displayed a reduction of 49.7 and 22.6% in cellulose content after saccharification of SB from an industry and SB from a fruit juice vendor, respectively. The effect of enzyme action on SB was further visualized by scanning electron microscopy and Fourier transform infra-red spectroscopy that showed increased porosity and a diminished peak for cellulose, indicating degradation of the substrate by the enzyme preparation.

Enhanced production of bacterial xylanase and its utility in saccharification of sugarcane bagasse

An investigation was carried out using sugarcane bagasse as the agricultural residue to study the optimization of xylanase production by solid-state fermentation. Maximum xylanase production (20.35 U/g substrate) was achieved by Bacillus substilis subsp. subtilis JJBS250 using 'one variable at a time approach' at pH 7.0, 40 °C after 48 h. After statistical optimization by response surface methodology (RSM) there was 4.82-fold improvement in xylanase production (98.16 U/g substrate). Further optimization of untreated and sodium carbonate pretreated sugarcane bagasse enzymatic hydrolysis was carried out using both bacterial (Bacillus substilis subsp. subtilis JJBS250) and fungal (Myceliophthora thermophila BJTLRMDU3) xylanases that showed high amount of reducing sugar liberation from untreated sugarcane bagasse (124.24 mg/g substrate) as compared to pretreated (76.23 mg/g substrate) biomass. Furthermore, biophysical characterization of untreated and sodium carbonate pretreated sugarcane bagasse using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM), revealed the structural changes in the pretreated biomass.

A Halotolerant Endo-1,4-β-Xylanase from Aspergillus clavatus with Potential Application for Agroindustrial Residues Saccharification

The use of non-potable water (such as seawater) is an attractive alternative for water intensive processes such as biomass pretreatment and saccharification steps in the production of biochemicals and biofuels. Identification and application of halotolerant enzymes compatible with high-salt conditions may reduce the energy needed for non-potable water treatment and decrease waste treatment costs. Here we present the biochemical properties of a halotolerant endo-1,4-β-xylanase produced by Aspergillus clavatus in submerged fermentation, using paper sludge (XPS) and sugarcane bagasse (XSCB), and its potential application in the hydrolysis of agroindustrial residues. The peptide mass fingerprint and amino acid sequencing of the XPS and XSCB enzymes showed primary structure similarities with an endo-1,4-β-xylanase from Aspergillus clavatus (XYNA_ASPCL). Both enzyme preparations presented good thermal stability at 50 °C and were stable over a wide range of pH and V_max up to 2450 U/mg for XPS. XPS and XSCB were almost fully stable even after 24 h of incubation in the presence of up to 3 M NaCl, and their activity were not affected by 500 mM NaCl. Both enzyme preparations were capable of hydrolyzing paper sludge and sugarcane bagasse to release reducing sugars. These characteristics make this xylanase attractive to be used in the hydrolysis of biomass, particularly with brackish water or seawater.

Sugarcane Bagasse as an Efficient Biosorbent for Methylene Blue Removal: Kinetics, Isotherms and Thermodynamics

Adsorption in biomass has proven to be a cost-effective option for treatment of wastewater containing dyes and other pollutants, as it is a simple and low cost technique and does not require high initial investments. The present work aimed to study the adsorption of methylene blue dye (MB) using sugarcane bagasse (SCB). The biomass was characterized by scanning electron microscopy (SEM). Adsorption studies were conducted batchwise. Kinetics, adsorption isotherms, and thermodynamics were studied. The results showed that SCB presented a maximum adsorption capacity of 9.41 mg g^-1 at 45 °C after 24 h of contact time. Adsorption kinetics data better fitted the pseudo-second order model, indicating a chemical process was involved. The Sips's three-parameter isotherm model was better for adjusting the data obtained for the adsorption isotherms, indicating a heterogeneous adsorption process. The process showed to be endothermic, spontaneous, and feasible. Therefore, it was concluded that SCB presented as a potential biosorbent material for the treatment of MB-contaminated waters.

Effects of Liquid Hot Water Combined with 1, 4-Butanediol on Chemical Composition and Structure of Moso Bamboo

The effects of liquid hot water combined with 1, 4-butanediol (LHW-BDO) on the chemical composition and structure of moso bamboo were investigated. The structure changes of moso bamboo fibers were characterized by infrared spectroscopy, X-ray diffraction, and electronic scanning electron microscopy. The results showed that the delignification rates of 1, 4-butanediol (BDO) and LHW-BDO pretreatment methods were at the same level (91.42-93.08%). However, compared with BDO pretreatment, the cellulose content in solid residue after LHW-BDO pretreatment was increased by 17.06% with a recovery rate of 75.68%, while the hemicellulose removal rate increased by 115.33% and reached 50.34%. After LHW-BDO pretreatment, the intramolecular hydrogen bonds, intermolecular hydrogen bonds, methylene bonds, and aromatic ether bonds of the fibers were broken, which contributed to the depolymerization and separation of cellulose, hemicellulose, and lignin molecules. However, LHW-BDO pretreatment does not destroy the β-glycoside bond which links the glucose molecule inside the fiber molecule, which was also beneficial to the separation of cellulose. In addition, the amorphous zone of bamboo fibers was destroyed by the above treatments, and the fiber structure of bamboo samples mostly exists in crystalline form. The crystallinity of bamboo pretreated with LHW-BDO was increased by 32.15%. It can be found by scanning electron microscopy that the surface of the pretreated bamboo samples showed uniformly distributed bubbly protuberance.

Advances in yeast alcoholic fermentations for the production of bioethanol, beer and wine

Yeasts have a long-standing relationship with humankind that has widened in recent years to encompass production of diverse foods, beverages, fuels and medicines. Here, key advances in the field of yeast fermentation applied to alcohol production, which represents the predominant product of industrial biotechnology, will be presented. More specifically, we have selected industries focused in producing bioethanol, beer and wine. In these bioprocesses, yeasts from the genus Saccharomyces are still the main players, with Saccharomyces cerevisiae recognized as the preeminent industrial ethanologen. However, the growing demand for new products has opened the door to diverse yeasts, including non-Saccharomyces strains. Furthermore, the development of synthetic media that successfully simulate industrial fermentation medium will be discussed along with a general overview of yeast fermentation modeling.

Overcoming challenges in lignocellulosic biomass pretreatment for second-generation (2G) sugar production: emerging role of nano, biotechnological and promising approaches

Production of green chemicals and biofuels in biorefineries is the potential alternative for petrochemicals and gasoline in transitioning of petro-economy into bioeconomy. However, an efficient biomass pretreatment process must be considered for the successful deployment of biorefineries, mainly for use of lignocellulosic raw materials. However, biomass recalcitrance plays a key role in its saccharification to obtain considerable sugar which can be converted into ethanol or other biochemicals. In the last few decades, several pretreatment methods have been developed, but their feasibility at large-scale operations remains as a persistent bottleneck in biorefineries. Pretreatment methods such as hydrodynamic cavitation, ionic liquids, and supercritical fluids have shown promising results in terms of either lignin or hemicellulose removal, thus making remaining carbohydrate fraction amenable to the enzymatic hydrolysis for clean and high amount of fermentable sugar production. However, their techno-economic feasibility at industrial scale has not been yet studied in detail. Besides, nanotechnological-based technologies could play an important role in the economically viable 2G sugar production in future. Considering these facts, in the present review, we have discussed the existing promising pretreatment methods for lignocellulosic biomass and their challenges, besides this strategic role of nano and biotechnological approaches towards the viability and sustainability of biorefineries is also discussed.

Deposition of lignin in four species of Saccharum

We used primers designed on conserved gene regions of several species to isolate the most expressed genes of the lignin pathway in four Saccharum species. S. officinarum and S. barberi have more sucrose in the culms than S. spontaneum and S. robustum, but less polysaccharides and lignin in the cell wall. S. spontaneum, and S. robustum had the lowest S/G ratio and a lower rate of saccharification in mature internodes. Surprisingly, except for CAD, 4CL, and CCoAOMT for which we found three, two, and two genes, respectively, only one gene was found for the other enzymes and their sequences were highly similar among the species. S. spontaneum had the highest expression for most genes. CCR and CCoAOMT B presented the highest expression; 4CL and F5H showed increased expression in mature tissues; C3H and CCR had higher expression in S. spontaneum, and one of the CADs isolated (CAD B) had higher expression in S. officinarum. The similarity among the most expressed genes isolated from these species was unexpected and indicated that lignin biosynthesis is conserved in Saccharum including commercial varieties Thus the lignin biosynthesis control in sugarcane may be only fully understood with the knowledge of the promotor region of each gene.

Development of co-immobilized tri-enzyme biocatalytic system for one-pot pretreatment of four different perennial lignocellulosic biomass and evaluation of their bioethanol production potential

Today, many researchers are focusing on research for alternative promising energy sources and sustainable technology for bioethanol production to meet the increasing global energy demand. Here, we develop a novel one-pot pretreatment technology by co-immobilizing laccase, cellulase and β-glucosidase to act as a tri-enzyme biocatalyst for evaluating the bioethanol production potential of four sustainable lignocellulosic biomasses viz., Typha angustifolia, Arundo donax, Saccharum arundinaceum, and Ipomoea carnea. The co-immobilized enzyme system was more stable at different temperatures and at longer storage, compared to free enzyme. During enzymatic saccharification, Saccharum arundinaceum showed higher total reducing sugar of 205 ± 3.73 mg/g when compared to other biomass. The highest percentage of bioethanol yield of 63.43 ± 9.35% was obtained with Ipomoea carnea. The effects of co-immobilized tri-enzyme biocatalyst on the biomasses were evaluated. The results revealed that the co-immobilized tri-enzyme biocatalyst could act as effective one-pot pretreatment for the production of bioethanol from lignocellulosic biomass.

Insights into the improvement of alkaline hydrogen peroxide (AHP) pretreatment on the enzymatic hydrolysis of corn stover: Chemical and microstructural analyses

The alkaline hydrogen peroxide (AHP) pretreatment (0.5 g H₂O₂/g corn stover, 30 °C, 24 h) removed 91.53% of the initial lignin and 55.77% of the initial hemicellulose in corn stover and afforded a considerable glucose yield (88.34%) through enzymatic hydrolysis. A combination of chemical and microstructural analyses was used to illustrate the mechanism of the effect of AHP pretreatment on enzymatic hydrolysis. During pretreatment, H₂O₂-derived radicals effectively spread into and destroyed the cell wall of various parts (vascular bundle sheath, xylem vessels, tracheid, phloem, and parenchyma) of corn stover to remove most of the lignin, acetyl group, and partial hemicellulose. They destroyed the compact structure of the cellulose-hemicellulose-lignin network, increased the cellulase-accessible pore volume by 6 times, doubled the area of exposed cellulose, and decreased the unproductive adsorption of enzymes onto lignin. Combining all the effects, AHP pretreatment effectively improved the cellulose accessibility to enhance the subsequent enzymatic hydrolysis efficiency.

Distinct polymer extraction and cellulose DP reduction for complete cellulose hydrolysis under mild chemical pretreatments in sugarcane

In this study, liquid hot water (LHW) and chemical (H₂SO₄, NaOH, CaO) pretreatments were performed in Saccharum species including sugarcane bagasse. In comparison, the LHW and CaO pretreatments significantly enhanced biomass enzymatic hydrolysis, leading to much high bioethanol yield obtained at 19% (% dry matter) with an almost complete hexoses-ethanol conversion in the desirable So5 bagasse sample. Despite the LHW and CaO are distinctive for extracting hemicellulose and lignin, both pretreatments largely reduced cellulose degree of polymerization for enhanced lignocellulose enzymatic saccharification. Further chemical analysis indicated that the pretreated So5 sample had much lower cellulose crystalline index, hemicellulosic Xyl/Ara and lignin S/H ratio than those of other biomass samples, which explained that the So5 had the highest bioethanol yield among Saccharum species. Therefore, a mechanism model was proposed to elucidate how mild pretreatments could enhance biomass enzymatic saccharification for a high bioethanol production in the desirable sugarcane bagasse.

Production of ethanol fuel from enzyme-treated sugarcane bagasse hydrolysate using d-xylose-fermenting wild yeast isolated from Brazilian biomes

In this study, we evaluated the potential of yeasts isolated from Amazon to produce second-generation ethanol from sugarcane bagasse delignified with alkaline hydrogen peroxide and hydrolysed with commercial enzyme preparation. The best efficiency savings in glucose and release of xylose were determined by considering the solids and enzyme loads. Furthermore, we selected Spathaspora passalidarum UFMG-CM-Y473 strain with the best fermentative parameters. Fermentations used bagasse hydrolysate without any nutritional supplementation, a significant difference from previous studies, which is closer to industrial conditions. Ethanol yield of 0.32 g/g and ethanol productivity of 0.34 g/L h were achieved after the consumption of 78% of the sugar. This hydrolysis/fermentation technology package could represent the input of an additional 3180 L of ethanol per hectare in areas of average sugarcane productivity such as 60 ton/ha. Thus, we concluded that Sp. passalidarum UFMG-CM-Y473 has a clear potential for the production of second-generation ethanol from delignified and enzyme-hydrolysed bagasse.

A new approach for bioethanol production from sugarcane bagasse using hydrodynamic cavitation assisted-pretreatment and column reactors

Hydrodynamic cavitation (HC) was adopted to assist alkaline-hydrogen peroxide pretreatment of sugarcane bagasse (SCB). In the following condition: 0.29 M of NaOH, 0.78% (v/v) of H₂O₂, 9.95 min of process time and 3 bar of inlet pressure, 95.4% of digestibility of cellulosic fraction was achieved. To take the best use of the pretreated biomass, the overall process was intensified by way of employing a packed bed flow-through column reactor and thus enabling to handle a high solid loading of 20%, thereby leading to cellulose and hemicellulose conversions to 74.7% and 75%, respectively. In the fermentation step, a bubble column reactor was introduced to maximize ethanol production from the pretreated SCB by Scheffersomyces stipitis NRRL-Y7124, resulting in 31.50 g/L of ethanol, 0.49 g/g of ethanol yield and 0.68 g/L.h of productivity. All this showed that our HC-assisted NaOH-H₂O₂ pretreatment strategy along with the process intensification approach might offer an option for SCB-based biorefineries.

Enzymatic hydrolysis of cactus pear varieties with high solids loading for bioethanol production

The optimization of enzymatic hydrolysis, with high solids loading, of two species of cactus pear for bioethanol production was tested evaluating the influence of surfactant Tween 80 and pretreatment with H₂O and H₂SO₄ (1% v/v) (50 °C, 150 rpm, 3 h). XRD and FTIR analyzes were performed. Afterwards, the influence of the factors cellulase (FPU g^-1), pectinase (U g^-1) and solids load (% w/v), on the hydrolysis of varieties (50 °C, 150 rpm, 48 h), and the fermentation of the optimal point (33 °C, 8 h) were evaluated. The pretreatments and the Tween 80 did not increase the hydrolysis yields and Rotacional Central Compound Design indicated that the pectinase factor was not significant. The best cellulase and solids load conditions were 10 FPU g^-1 of biomass and 30% w/v for both species. The fermentation efficiency of hydrolysates for Nopalea cochenillifera and Opuntia ficus-indica were 76.3% and 82.8%, respectively, showing their potential for bioethanol production.

Characterization of cellulase from Aspergillus tubingensis NKBP-55 for generation of fermentable sugars from agricultural residues

The aim of this work was to characterize cellulase from Aspergillus tubingensis NKBP-55 for generation of fermentable sugars from agricultural residues. The strain produced high titres of cellulase (750 U/gds) on copra meal in solid state fermentation (SSF). The enzyme preparation also showed hemicellulolytic activities (U/gds) viz. endo-mannanase (1023), endo-xylanase (167), β-glucosidase (72) and α-galactosidase (54). Zymography revealed presence of six cellulases, six mannanases and one β-glucosidase. It effectively degraded sugarcane bagasse (SCB) and rice straw (RS) releasing xylose, glucose and cellobiose. One cellulase (Cat 1, Mr ∼65 kDa) was purified and characterized. It retained more than 50% activity at 70 °C after 150 mins and its activity was enhanced in the presence of Mn²⁺ ions (130%) and β-mercaptoethanol (140%). FTIR and ¹³C CP/MAS NMR analysis of the enzyme treated SCB and RS revealed degradation of cellulose and hemicellulose, while ¹H and ¹³C liquid state NMR experiments confirmed release of glucose.

Biosurfactants produced by Scheffersomyces stipitis cultured in sugarcane bagasse hydrolysate as new green larvicides for the control of Aedes aegypti, a vector of neglected tropical diseases

Biosurfactants are microbial metabolites with possible applications in various industrial sectors that are considered ecofriendly molecules. In recent years, some studies identified these compounds as alternatives for the elimination of vectors of tropical diseases, such as Aedes aegypti. The major bottlenecks of biosurfactant industrial production have been the use of conventional raw materials that increase production costs as well as opportunistic or pathogenic bacteria, which restrict the application of these biomolecules. The present study shows the potential of hemicellulosic sugarcane bagasse hydrolysate as a raw material for the production of a crystalline glycolipidic BS by Scheffersomyces stipitis NRRL Y-7124, which resulted in an emulsifying index (EI24) of 70 ± 3.4% and a superficial tension of 52 ± 2.9 mN.m-1. Additionally, a possible new application of these compounds as biolarvicides, mainly against A. aegypti, was evaluated. At a concentration of 800 mg.L-1, the produced biosurfactant caused destruction to the larval exoskeletons 12 h after application and presented an letal concentration (LC50) of 660 mg.L-1. Thus, a new alternative for biosurfactant production using vegetal biomass as raw material within the concept of biorefineries was proposed, and the potential of the crystalline glycolipidic biosurfactant in larvicidal formulations against neglected tropical disease vectors was demonstrated.

Potential of oleaginous yeast Trichosporon sp., for conversion of sugarcane bagasse hydrolysate into biodiesel

This study reports production of microbial oil from a yeast strain Trichosporon sp., (RW) isolated from decayed wood. Preliminary analysis based on fluorescence microscopy and spectroscopy of Nile red stained yeast cells showed accumulation of lipid globules. The potential of the yeast to produce lipids was evaluated on glucose, glycerol and acid hydrolysate of sugarcane bagasse, where Trichosporon sp. (RW) was found to accumulate 21.45 (59.6%), 18.41 (56%) and 10.25g/l (40.5%) of the lipids after 120h of fermentation at 30°C. FAME analysis of lipids by GC-FID and NMR revealed oleic acid (18:1) as the major constituent, corresponding to 50.05, 46.48 and 54.66% of the accumulated lipids in glucose, glycerol and hydrolysate grown cultures, respectively. Other accumulated lipids included palmitic (16:0), linoleic (18:2) and stearic acids (18:0) in that order. The cetane number of the lipids ranged from 52.39 to 59.57 indicating suitability for biodiesel production.