Energy-efficient glucose recovery from chestnut shell by optimization of NaOH pretreatment at room temperature and application to bioethanol production.

Biofuel policies are currently being implemented globally to reduce greenhouse gas emissions. The recent European regulation, Renewable Energy Directive (RED) II, states that renewable resources should be used as raw materials. In this study, chestnut shell (CNS), a food processing residue, was utilized as a feedstock for bioethanol production. Statistical optimization was performed to improve biomass-to-glucose conversion (BtG) from the CNS. In order to design an energy-efficient process, the pretreatment was fixed at room temperature in the numerical optimization. The optimal conditions derived from the predicted model are as follows: temperature of 25 °C, reaction time of 2.8 h, and NaOH concentration of 1.9% (w/w). Under optimal conditions, both predicted and experimental BtG were 31.0%, while BtG was approximately 3.3-fold improved compared to the control group (without pretreatment). The recovered glucose was utilized for bioethanol fermentation by Saccharomyces cerevisiae K35 and the ethanol yield was achieved to be 98%. Finally, according to the mass balance based on 1000 g CNS, glucose of 310 g can be recovered by the pretreatment; the bioethanol production was approximately 155 g. This strategy suggests a direction to utilize CNS as a potential feedstock for biorefinery through the design of an economical and energy-efficient pretreatment process by lowering the reaction temperature to room temperature.

Valorisation of keratin waste: Controlled pretreatment enhances enzymatic production of antioxidant peptides.

Conversion of keratin waste to value-added products not only reduces waste volumes but also creates new revenue streams for the animal production industry. In the present study, combination of alkaline pretreatment of cattle hair with enzymatic hydrolysis was studied to produce keratin hydrolysates with relatively high antioxidant activities. Firstly, the effect of pretreatment conditions at a high solid/liquid mass ratio of 1:2 with different NaOH loadings and temperatures was studied. Increasing NaOH concentration from 1.0% to 2.5% and temperature from room temperature to 110 °C increased hair hydrolysis by keratinase and protein recovery in hydrolysates. Mild pretreatment with 1.5% NaOH at 70 °C for 30 min led to a protein recovery of 30% in the enzymatic hydrolysate. The resulting hydrolysate showed a high antioxidant activity, scavenging 69% of the ABTS radical with a low EC50 of 0.8 mg/mL. Severe pretreatment with 2.5% NaOH at 110 °C for 30 min resulted in a higher protein recovery of 45%, but a lower ABTS radical scavenging activity of 56% and a higher EC50 of 1.3 mg/mL. The reduced antioxidant activity was attributed to the reduced proportion of small peptides (<3 kDa) and the increased extent of amino acid chemical modification. This study demonstrated that controlling alkali pretreatment conditions could lead to the production of enzymatic hydrolysates with higher antioxidant activities for potential value-adding applications. The information generated from this study will aid scale-up and commercialisation of processes with optimised antioxidant peptide production.

Simultaneous study of the interaction effect of chemical and hydrothermal pretreatment on the yield of methane produced from municipal waste.

Municipal waste has the potential to be a significant source of energy production. This study investigated pretreatment methods such as NaOH, hydrothermal, and ozonation to increase biomethane production from municipal waste. In addition, these pretreatments were further evaluated using ultrasonic pretreatment after achieving optimal conditions by RSM CCD methods. The optimum pretreatment conditions were observed to be 8% NaOH concentration, 132 °C hydrothermal temperature, and O3 equal to 0.19 g/g TS. The maximum biomethane produced and achieved during the tests was 394 mL/kg TS, which increased to 410 mL/kg TS after ultrasonic pretreatment. The best sCOD reduction in the optimal pretreatment conditions and after the ultrasonic pretreatment was 87% and 91%, respectively. Also, in the absence of ozone pretreatment, the highest yields of biomethane and biogas occurred at a 6.4% concentration of NaOH and a temperature of 135 °C; however, in the presence of ozone, the yield of biomethane and biogas produced was greater and the inhibitory effect of sodium hydroxide also occurs in higher amounts. Experiments have shown that ozonation increases biomethane production rather than increasing biogas production (hence the ratio of methane to biogas).

Biogas Production from Sunflower Head and Stalk Residues: Effect of Alkaline Pretreatment.

Sunflower residues are considered a prominent renewable source for biogas production during anaerobic digestion (AD). However; the recalcitrant structure of this lignocellulosic substrate requires a pretreatment step for efficient biomass transformation and increased bioenergy output. The aim of the present study was to assess the effect of alkaline pretreatment of various parts of the sunflower residues (e.g., heads and stalks) on their methane yield. Experimental data showed that pretreatment at mild conditions (55 °C; 24 h; 4 g NaOH 100 g-1 total solids) caused an increase in the biochemical methane potential (BMP) of both heads and stalks of the sunflower residues as determined in batch tests. The highest methane production (268.35 ± 0.11 mL CH4 g-1 volatile solids) was achieved from the pretreated sunflower head residues. Thereafter; the effect of alkaline pretreatment of sunflower head residues was assessed in continuous mode; using continuous stirred-tank reactors (CSTRs) under two operational phases. During the first phase; the CSTRs were fed with the liquid fraction produced from the pretreatment of sunflower heads. During the second phase; the CSTRs were fed with the whole slurry resulting from the pretreatment of sunflower heads (i.e., both liquid and solid fractions). In both operating phases; it was observed that the alkaline pretreatment of the sunflower head residues had a negligible (phase I) or even a negative effect on biogas production; which was contradictory to the results of the BMP tests. It seems that; during alkaline pretreatment; this part of the sunflower residues (heads) may release inhibitory compounds; which induce a negative effect on biogas production in the long term (e.g., during continuously run digesters such as CSTR) but not in the short-term (e.g., batch tests) where the effect of the inoculum may not permit the inhibition to be established.

Importance of "weak-base" poplar wastes to process performance and methane yield in solid-state anaerobic digestion.

Failure of methane yield is common for anaerobic digestion (AD) of "weak-acid/acid" wastes alone. In order to verify the importance of pH of materials on the process performance and the methane yield, the "weak-base" wastes-poplar wastes (PW) were used as substrate of solid-state AD (SS-AD). The results show that PW could be used for efficient methane yield after NaOH treatment, the total methane yield was 81.1 L/kg volatile solids (VS). PW also could be used for anaerobic co-digestion with high-pH cattle slurry (CM). For the group with NaOH pretreatment, time used for reaching stable state was 2 days earlier than that of the group without NaOH pretreatment. The maximal methane yield of 98.2 L/kg VS was obtained on conditions of 1:1 of PW-to-CM (P/C) ratio and NaOH pretreatment, which was 21.1% (p < 0.05) higher than that of PW. The maximal reductions of total solids (TS), VS, cellulose and hemicellulose were 51.3%, 57.5%, 46.0% and 47.0%, respectively, which were associated with the maximal methane yield. The results indicate that PW could be alone used for efficient SS-AD for methane yield after NaOH treatment.

Improvement of radio frequency (RF) heating-assisted alkaline pretreatment on four categories of lignocellulosic biomass.

Pretreatment plays an important role in making the cellulose accessible for enzyme hydrolysis and subsequent conversion because it destroys more or less resistance and recalcitrance of biomass. Radio frequency (RF)-assisted dielectric heating was utilized in the alkaline pretreatment on agricultural residues (corn stover), herbaceous crops (switchgrass), hardwood (sweetgum) and softwood (loblolly pine). Pretreatment was performed at 90 °C with either RF or traditional water bath (WB) heating for 1 h after overnight soaking in NaOH solution (0.2 g NaOH/g Biomass). Pretreated materials were characterized by chemical compositional analysis, enzyme hydrolysis, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The glucan yields of RF-heated four categories of hydrolysates were 89.6, 72.6, 21.7, and 9.9 %. Interestingly, RF heating raised glucan yield on switchgrass and sweetgum but not on corn stover or loblolly pine. The SEM images and FTIR spectra agreed with results of composition analysis and hydrolysis. GC-MS detected some compounds only from RF-heated switchgrass. These compounds were found by other researchers only in high-temperature (150-600 °C) and high-pressure pyrolysis processes.

Biochemical methane potential, biodegradability, alkali treatment and influence of chemical composition on methane yield of yard wastes.

In this study, the biochemical CH4 potential, rate, biodegradability, NaOH treatment and the influence of chemical composition on CH4 yield of yard wastes generated from seven trees were examined. All the plant parts were sampled for their chemical composition and subjected to the biochemical CH4 potential assay. The component parts exhibited significant variation in biochemical CH4 potential, which was reflected in their ultimate CH4 yields that ranged from 109 to 382 ml g(-1) volatile solids added and their rate constants that ranged from 0.042 to 0.173 d(-1). The biodegradability of the yard wastes ranged from 0.26 to 0.86. Variation in the biochemical CH4 potential of the yard wastes could be attributed to variation in the chemical composition of the different fractions. In the Thespesia yellow withered leaf, Tamarindus fruit pericarp and Albizia pod husk, NaOH treatment enhanced the ultimate CH4 yields by 17%, 77% and 63%, respectively, and biodegradability by 15%, 77% and 61%, respectively, compared with the untreated samples. The effectiveness of NaOH treatment varied for different yard wastes, depending on the amounts of acid detergent fibre content. Gliricidia petals, Prosopis leaf, inflorescence and immature pod, Tamarindus seeds, Albizia seeds, Cassia seeds and Delonix seeds exhibited CH4 yields higher than 300 ml g(-1) volatile solids added. Multiple linear regression models for predicting the ultimate CH4 yield and biodegradability of yard wastes were designed from the results of this work.

Biogas production from Pongamia biomass wastes and a model to estimate biodegradability from their composition.

In this study, I investigated the chemical characteristics, biochemical methane potential, conversion kinetics and biodegradability of untreated and NaOH-treated Pongamia plant parts, and pod husk and press cake from the biodiesel industry to evaluate their suitability as an alternative feedstock for biogas production. The untreated Pongamia seeds exhibited the maximum CH4 yield of 473 ml g (-1) volatile solid (VS) added. Yellow, withered leaves gave a yield as low as 122 ml CH4 g (-1) VS added. There were significant variations in the CH4 production rate constants, which ranged from 0.02 to 0.15 d (-1), and biodegradability, which ranged from 0.25 to 0.98. NaOH treatment of leaf and pod husk, which were highly rich in fibers, increased the yields by 15-22% and CH4 production rate constants by 20-75%. Utilization of Pongamia wastes in biogas digesters not only influences the economics of biodiesel production but also yields CH4 fuel and protects the environment. The experimental data from this study were used to develop a multiple regression model, which could estimate biodegradability based on biochemical characteristics. The model predicted the biodegradability of previously published biomass wastes (r(2) = 0.88) from their biochemical composition. The theoretical CH4 yields estimated as 350 ml g(-1) chemical oxygen demand destroyed are much higher than the experimental yields as 100% biodegradability is assumed for each substrate. Upon correcting the theoretical CH4 yields with biodegradability data obtained from chemical analyses of substrates, their ultimate CH4 yields could be predicted rapidly.

Enhancing biomass conservation and enzymatic hydrolysis of sweet sorghum bagasse by combining pretreatment with ensiling and NaOH.

Lignocellulosic pretreatment is an important stage in biomass utilization, which usually requires high input. In this study, a low-cost method using combined ensiling and NaOH was developed for lignocellulosic pretreatment. Sweet sorghum bagasse (SSB) was ensiled for 21 days and then treated with diluted NaOH (0%, 1%, and 2%) for fermentation. The results showed that the application of Lactobacillus plantarum (L) reduced fermentation losses of the silages, mainly low water-soluble carbohydrate (WSC) and ammonia nitrogen loss. Meanwhile, the application of Lactobacillus plantarum and ensiling enzyme (LE) promoted lignocellulosic degradation, as evidenced by low neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (ADL), and hemicellulosic (HC) contents. The dominant bacterial genera were Lactobacillus, uncultured_bacterium_f_Enterobacteriaceae, and Pantoea after silage, which corresponded to the higher lactic acid and acetic contents and lower pH. The reducing sugar yields of SSB increased after combined pretreatment of silage and NaOH and were further enhanced by the 2% NaOH application, as evidenced by the high reducing sugar yield and microstructure damage, especially in the L-2% NaOH group and the LE-2% NaOH group, in which the reducing sugar yields were 87.99 and 94.45%, respectively, compared with those of the no additive control (CK)-0 NaOH group. Therefore, this study provides an effective method for SSB pretreatment to enhance biomass conservation.

Physicochemical Pretreatment of Vietnamosasa pusilla for Bioethanol and Xylitol Production.

The consumption of fossil fuels has resulted in severe environmental consequences, including greenhouse gas emissions and climate change. Therefore, transitioning to alternative energy sources, such as cellulosic ethanol, is a promising strategy for reducing environmental impacts and promoting sustainable low-carbon energy. Vietnamosasa pusilla, an invasive weed, has been recognized as a high potential feedstock for sugar-based biorefineries due to its high total carbohydrate content, including glucan (48.1 ± 0.3%) and xylan (19.2 ± 0.4%). This study aimed to examine the impact of NaOH pretreatment-assisted autoclaving on V. pusilla feedstock. The V. pusilla enzymatic hydrolysate was used as a substrate for bioethanol and xylitol synthesis. After treating the feedstock with varying concentrations of NaOH at different temperatures, the glucose and xylose recovery yields were substantially higher than those of the untreated material. The hydrolysate generated by enzymatic hydrolysis was fermented into bioethanol using Saccharomyces cerevisiae TISTR 5339. The liquid byproduct of ethanol production was utilized by Candida tropicalis TISTR 5171 to generate xylitol. The results of this study indicate that the six- and five-carbon sugars of V. pusilla biomass have great potential for the production of two value-added products (bioethanol and xylitol).

Efficient Cationization of Cotton for Salt-Free Dyeing by Adjusting Fiber Crystallinity through Alcohol-Water-NaOH Pretreatment.

Cationization of cotton is considered to be an effective way to realize salt-free dyeing of reactive dyes. However, applying cotton modified with glycidyltrimethylammonium chloride (GTA) suffers from large consumption of the cationic reagent. One of the reasons is that high crystallinity of cotton fibers hinders the penetration of the reagents into the cellulose interior and limits the reaction between them. This paper designed to use alcohol-water-NaOH system to pretreat the fibers before cationization. With this method, crystallinity of the cotton fibers is decreased and more reactive -OH is exposed, resulting in much higher fiber-reagent reactivity and increased GTA utilization. Influence of alcohol type, alcohol-to-water ratio, and quantity of NaOH on fiber crystallinity and GTA dosage for cationization are all examined. It is found that for achieving 96.0% fixation of C.I. Reactive Black 5 in the absence of salt, GTA dosage can be reduced by half when the fibers are pretreated by alcohol-water-NaOH. Compared with ethanol, n-propanol and isopropanol, tert-butyl alcohol incorporated system shows better performance in increasing fiber reactivity due to their weaker ability to dissolve ions. In this study, XRD and FT-IR are used to demonstrate changes in crystallinity of the fibers after pretreatment. The alteration in micromorphology and hydrophilicity of the pretreated fibers is observed by SEM and water contact angle test, respectively. Furthermore, the alcohol-water-NaOH system can be recycled to show very good repeatability. Notably, all dyed samples pretreated with the system present high color saturation and satisfactory color fastness, especially that the wet rub fastness reaches 4-5 grade, which is one grade higher than that obtained from the conventional dyeing with salt. The above findings prove that alcohol-water-NaOH pretreatment is effective in enhancing reactivity of the cotton fibers and penetrability of the agent, and it shows promising prospects in real application.

Effect of combined wet alkaline mechanical pretreatment on enzymatic hydrolysis of corn stover and its mechanism.

BACKGROUND: To further optimize the mechanochemical pretreatment process, a combined wet alkaline mechanical pretreatment of corn stover was proposed with a short time and less chemical consumption at room temperature. RESULTS: The combined alkaline mechanical pretreatment significantly enhanced enzymatic hydrolysis resulting a highest glucose yield (YG) of 91.9% with 3% NaOH and ball milling (BM) for 10 min. At this optimal condition, 44.4% lignin was removed and major portion of cellulose was retained (86.6%). The prehydrolysate contained by-products such as monosaccharides, oligosaccharides, acetic acid, and lignin but no furfural and 5-HMF. The alkaline concentration showed a significant impact on glucose yield, while the BM time was less important. Quantitative correlation analysis showed that YG (%) = 0.68 × BM time (min) + 19.27 × NaOH concentration (%) + 13.71 (R2 = 0.85), YG = 6.35 × glucan content - 231.84 (R2 = 0.84), and YG = - 14.22 × lignin content + 282.70 (R2 = 0.87). CONCLUSION: The combined wet alkaline mechanical pretreatment at room temperature had a boosting effect on the yield of enzymatic hydrolysis with short treatment time and less chemical consumption. The impact of the physical and chemical properties of corn stover pretreated with different BM times and/or different NaOH concentrations on the subsequent enzymatic hydrolysis was investigated, which would be beneficial to illustrate the effective mechanism of the mechanochemical pretreatment method.

Green Deal and Circular Economy of Bottom Ash Waste Management in Building Industry-Alkali (NaOH) Pre-Treatment.

This study aims to investigate the possibilities of municipal waste incineration bottom ash (MSWIBA) utilization in the construction sector. MSWIBA development fits into the European Green Deal, Sustainable Development Goals (SDGs), and the Circular Economy (CE). This manuscript describes current MSWIBA treatment such as solidification, ceramization, vitrification, chemical activation (NaOH, CaOH2, NA2SiO3 + NaOH, Na2CO3 + NaOH, NH4OH), acid treatment with diluted solutions (HCl, H2SO4), chemical stabilization (FeSO4, PO43-), chelation, etc. For the purpose of comparative research, MSWIBA before valorization, after valorization, and after NaOH pre-treatment was investigated. In terms of their physico-chemical properties, the tested samples were examined. Three kinds of MSWIBA were used as a substitute for 30% of cement in mortars. The mortars were tested for 28-day strength. Leachability tests were performed in acid, aggressive, alkali, and neutral water environments. Life Cycle Assessment (LCA) analysis was carried out, which presented the environmental benefits of MSWIBA management in construction.

Alkali pretreatment of wheat straw followed by microbial hydrolysis for bioethanol production.

The combination of NaOH pretreatment and microorganisms isolated from termite was used for releasing wrapped polysaccharides from wheat straw biomass matrix. Different concentrations of NaOH (1%, 3%, 5%, 7% and 10%) were considered to remove lignin and to release polysaccharides as a pretreatment method at 80°C for 4 h before subjecting it to microbial hydrolysis. Data obtained from compositional analysis of pretreated wheat straws show that a significant amount of cellulose and lignin were released after NaOH pretreatments. The amount of cellulose and lignin released was increased with increasing concentration of NaOH in the pretreatment solution. Further analysis of X-Ray diffraction, field emission scanning electron microscope and Fourier transform infrared spectroscopy confirms the removal of lignin and release of cellulose. About 69.5% of lignin was solubilized and 72.67% of cellulose was released after 10% NaOH pretreatment which was the maximum. Data from spectrophotometric analysis of reducing sugar by the 3,5-dinitrosalycilic acid method show that 83.68% (0.706 g/100 ml) of polysaccharides were converted to glucose and xylose by isolated bacteria after the 15th day of hydrolysis.

Feasibility of anaerobic digestion on the release of biogas and heavy metals from rice straw pretreated with sodium hydroxide.

The feasibility of anaerobic digestion on the release of biogas and heavy metals from contaminated rice straw pretreated with NaOH solution was studied. The results show that NaOH pretreatment can significantly boost the release of biogas and heavy metals from rice straw using anaerobic digestion. Under the optimal conditions for biomass pretreated 6% (w/w) NaOH with a solid-to-solution ratio of 1:20, total biogas and methane yields of 446.3 mL/g and 263.5 mL/g volatile solids were achieved, which were 22.18% and 41.59% higher than those of the control without NaOH pretreatment, respectively, and the release percentages of Cd, Pb, Cu, and Zn from rice straw reached 86.95-97.69%. The release of heavy metals from rice straw can contribute to both the degradation of lignin by NaOH pretreatment and the utilization/transformation of lignocellulose via anaerobic digestion. The acidification levels and total volatile fatty acid contents significantly influence on the release of heavy metals. Based on the Illumina HiSeq sequencing analysis, the dominant phyla in the biogas residues were proteolytic (Bacteroidetes) and hydrogen-producing (Firmicutes) bacteria, while the growth of Methanospirillum and Methanosaeta in anaerobically digested effluent was promoted. The results revealed that anaerobic digestion combined with NaOH pretreatment is suitable for the disposal of heavy metal-contaminated biomass.

Sodium Hydroxide Pretreatment as an Effective Approach to Reduce the Dye/Holes Recombination Reaction in P-Type DSCs.

We report the synthesis of a novel squaraine dye (VG21-C12) and investigate its behavior as p-type sensitizer for p-type Dye-Sensitized Solar Cells. The results are compared with O4-C12, a well-known sensitizer for p-DSC, and sodium hydroxide pretreatment is described as an effective approach to reduce the dye/holes recombination. Various variable investigation such as dipping time, dye loading, photocurrent, and resulting cell efficiency are also reported. Electrochemical impedance spectroscopy (EIS) was utilized for investigating charge transport properties of the different photoelectrodes and the recombination phenomena that occur at the (un)modified electrode/electrolyte interface.

Improving the methane yield of maize straw: Focus on the effects of pretreatment with fungi and their secreted enzymes combined with sodium hydroxide.

In order to improve the methane yield, the alkaline and biological pretreatments on anaerobic digestion (AD) were investigated. Three treatments were tested: NaOH, biological (enzyme and fungi), and combined NaOH with biological. The maximum reducing sugar concentrations were obtained using Enzyme T (2.20 mg/mL) on the 6th day. The methane yield of NaOH + Enzyme A was 300.85 mL/g TS, 20.24% higher than the control. Methane yield obtained from Enzyme (T + A) and Enzyme T pretreatments were 277.03 and 273.75 mL/g TS, respectively, which were as effective as 1% NaOH (276.16 mL/g TS) in boosting methane production, and are environmentally friendly and inexpensive biological substitutes. Fungal pretreatment inhibited methane fermentation of maize straw, 15.68% was reduced by T + A compared with the control. The simultaneous reduction of DM, cellulose and hemicellulose achieved high methane yields. This study provides important guidance for the application of enzymes to AD from lignocellulosic agricultural waste.

Replacing process water and nitrogen sources with biogas slurry during cellulosic ethanol production.

BACKGROUND: Environmental issues, such as the fossil energy crisis, have resulted in increased public attention to use bioethanol as an alternative renewable energy. For ethanol production, water and nutrient consumption has become increasingly important factors being considered by the bioethanol industry as reducing the consumption of these resources would decrease the overall cost of ethanol production. Biogas slurry contains not only large amounts of wastewater, but also the nutrients required for microbial growth, e.g., nitrogen, ammonia, phosphate, and potassium. Therefore, biogas slurry is an attractive potential resource for bioethanol production that could serve as an alternative to process water and nitrogen sources. RESULTS: In this study, we propose a method that replaces the process water and nitrogen sources needed for cellulosic ethanol production by Zymomonas mobilis with biogas slurry. To test the efficacy of these methods, corn straw degradation following pretreatment with diluted NaOH and enzymatic hydrolysis in the absence of fresh water was evaluated. Then, ethanol fermentation using the ethanologenic bacterial strain Z. mobilis ZMT2 was conducted without supplementing with additional nitrogen sources. After pretreatment with 1.34% NaOH (w/v) diluted in 100% biogas slurry and continuous enzymatic hydrolysis for 144 h, 29.19 g/L glucose and 12.76 g/L xylose were generated from 30 g dry corn straw. The maximum ethanol concentration acquired was 13.75 g/L, which was a yield of 72.63% ethanol from the hydrolysate medium. Nearly 94.87% of the ammonia nitrogen was depleted and no nitrate nitrogen remained after ethanol fermentation. The use of biogas slurry as an alternative to process water and nitrogen sources may decrease the cost of cellulosic ethanol production by 10.0-20.0%. By combining pretreatment with NaOH diluted in biogas slurry, enzymatic hydrolysis, and ethanol fermentation, 56.3 kg of ethanol was produced by Z. mobilis ZMT-2 through fermentation of 1000 kg of dried corn straw. CONCLUSIONS: In this study, biogas slurry replaced process water and nitrogen sources during cellulosic ethanol production. The results suggest that biogas slurry is a potential alternative to water when pretreating corn straw and, thus, has important potential applications in cellulosic ethanol production from corn straw. This study not only provides a novel method for utilizing biogas slurry, but also demonstrates a means of reducing the overall cost of cellulosic ethanol.

Prospecting Agro-waste Cocktail: Supplementation for Cellulase Production by a Newly Isolated Thermophilic B. licheniformis 2D55.

Bacteria isolated from thermophilic environment that can produce cellulase as well as utilise agro-waste biomass have a high potential for developing thermostable cellulase required in the biofuel industry. The cost for cellulase represents a significant challenge in converting lignocellulose to fermentable sugars for biofuel production. Among three potential bacteria examined, Bacillus licheniformis 2D55 (accession no. KT799651) was found to produce the highest cellulolytic activity (CMCase 0.33 U/mL and FPase 0.09 U/mL) at 18-24 h fermentation when grown on microcrystalline cellulose (MCC) as a carbon source in shake flask at 50 °C. Cellulase production process was further conducted on the untreated and NaOH pretreated rice straw (RS), rice husk (RH), sugarcane bagasse (BAG) and empty fruit bunch (EFB). Untreated BAG produced the highest FPase (0.160 U/mL), while the highest CMCase (0.150 U/mL) was supported on the pretreated RH. The mixture of untreated BAG and pretreated RH as agro-waste cocktail has remarkably improved CMCase (3.7- and 1.4-fold) and FPase (2.5- and 11.5-fold) compared to the untreated BAG and pretreated RH, respectively. The mechanism of cellulase production explored through SEM analysis and the location of cellulase enzymes of the isolate was also presented. Agro-waste cocktail supplementation provides an alternative method for an efficient production of cellulase.

Pretreatment of bamboo by ultra-high pressure explosion with a high-pressure homogenizer for enzymatic hydrolysis and ethanol fermentation.

Bamboo shoots, 2- and 5-year-old bamboo were treated by using a homogenizer in a constant suspended state, a process termed as ultra-high pressure explosion (UHPE). The bamboo powder was heated in 2% NaOH solution at 121°C, and then 100MPa UHPE-treated through a homogenizer. The results verified that UHPE changed the suspension solution of powder into a stick fluid. The contents of lignin were decreased significantly. The bamboo shoots and 2-year-old bamboo were completely hydrolyzed to glucose within 48h by enzymes loading of 15 FPU of cellulase and 30IU of ß-glucosidase per gram glucan. Fermentation of enzymatic hydrolyzates with Saccharomyces cerevisiae resulted in about 89.7-95.1% of the theoretical ethanol yield after 24h. Therefore, NaOH+UHPE is argued to be a potential alternative technology for pretreatment of bamboo.