Hemicellulosic Hydrolysate Research Articles

Enhanced Tolerance of Spathaspora passalidarum to Sugarcane Bagasse Hydrolysate for Ethanol Production from Xylose.

During the pretreatment and hydrolysis of lignocellulosic biomass to obtain a hydrolysate rich in fermentable sugars, furaldehydes (furfural and hydroxymethylfurfural), phenolic compounds, and organic acids are formed and released. These compounds inhibit yeast metabolism, reducing fermentation yields and productivity. This study initially confirmed the ability of Spathaspora passalidarum to ferment xylose and demonstrated its sensibility to the inhibitors present in the hemicellulosic sugarcane bagasse hydrolysate. Then, an adaptive laboratory evolution, with progressive increments of hydrolysate concentration, was employed to select a strain more resistant to hydrolysate inhibitors. Afterward, a central composite design was performed to maximize ethanol production using hydrolysate as substrate. At optimized conditions (initial cell concentration of 30 g/L), S. passalidarum was able to produce 19.4 g/L of ethanol with productivity, yield, and xylose consumption rate of 0.8 g/L.h and 0.4 g/g, respectively, in a sugarcane bagasse hemicellulosic hydrolysate. A kinetic model was developed to describe the inhibition of fermentation by substrate and product. The values obtained for substrate saturation and inhibition constant were Ks = 120.4 g/L and Ki = 1293.4 g/L. Ethanol concentration that stops cell growth was 30.1 g/L. There was an agreement between simulated and experimental results, with a residual standard deviation lower than 6%.

Optimization of activated charcoal detoxification and concentration of chestnut shell hydrolysate for xylitol production.

To increase xylose concentration of the chestnut shell hemicellulosic hydrolysate with an acceptable phenolic compound level in order to enhance xylitol production by Candida tropicalis M43. The xylose concentration and total phenolic compound concentration of the hydrolysate were obtained as 33.68g/L and 77.38mg gallic acid equivalent/L, respectively by optimization of detoxification parameters and concentration level (60°C, 115min contact time, 5.942% (w/v) dosage of activated charcoal, 120 strokes/min shaking rate and 0.2 volume ratio). Xylitol production was achieved in the hydrolysate by using Candida tropicalis M43. The maximum xylitol concentration was 6.30g/L and productivity, yield and percentage of substrate conversion were calculated as 0.11g/L h, 19.13% and 97.79%, respectively. In addition, the chestnut shell hydrolysate fortified with xylose and the maximum xylitol concentration increased to 18.08g/L in the hydrolysate-based medium containing 80g/L xylose. Optimizing detoxification conditions with concentration level was found to be useful for enhancing xylitol production. In addition, fortification of the hydrolysate caused a three fold increase in maximum xylitol concentration.

A flow-through reactor for fast fractionation and production of structure-preserved lignin

Viable biorefinery requires a robust and cost-competitive method of biomass fractionation. Here, we design green and efficient flow-through reactor for biomass fractionation. Aqueous formic acid was used as a solvent at mild temperatures. The time course study verified a rapid flow-through fractionation of wheat straw in 20 min at 130 °C involving synergetic actions of acid hydrolysis of hemicellulose and lignin dissolution. The obtained fractionation attained 76.3 % of lignin yield and 69.8 % of sugars yield without measurable degradation of hemicelluloses. More importantly, lignin fractionation showed well-preserved inter-unit linkages as indicated by the 76.4 % retention of aryl ether bond. The exponential model was established and well described the relationships between fractionation conditions and kinetics of lignin solubilization. This rapid flow-through reactor/fractionation promises to be a very practical equipment/strategy for biomass fractionation with competitive products.

Towards a wheat straw biorefinery: Combination of Organosolv and Liquid Hot Water for the improved production of sugars from hemicellulose and lignin hydrolysis

One major challenge of sustainable biorefineries relies on valorizing hemicellulose and lignin simultaneously. However, a single pretreatment will unlikely render high sugar and lignin yields. Liquid-Hot-Water (LHW) and Organosolv (OS) highlight as technologies to solubilize these components (in different proportions). A combined pretreatment may hydrolyze lignin and hemicellulose into different fractions, with higher overall yield and leaving cellulose available for further processing. Hence, it must be determined the stages' order to maximize hemicellulose/lignin hydrolysis. We performed both configurations (OS → LHW and LHW → OS) using wheat straw and determined sugar and lignin concentration and the dissolved lignin's molar-mass distributions. Both configurations reached similar sugar concentrations (~12 g/L), but LHW → OS reached a 1.6-times higher lignin extraction (7 to 11 g/L in the OS-stage). The extracted lignin molar mass in LHW → OS had lower polydispersity and molar-mass averages, favoring colloidal particle production. These results bring us closer to a sustainable biorefinery valorizing the different feedstock fractions.

Exploiting the Non-conventional Yeast Spathaspora passalidarum as a Platform for Hemicellulosic Hydrolysate Conversion into Bioproducts: a Mini Review

Bioethanol from lignocellulosic biomass (namely second-generation bioethanol) has been considered to be a great opportunity to increase production of biofuels from renewable sources without expanding the world planted area. Spathaspora passalidarum has shown great potential to convert sugars derived from lignocellulosic materials, which comprises hexoses and pentoses, into bioethanol. Besides its unusual ability to produce ethanol naturally from pentoses, this microorganism can also be used to obtain other products of interest. This review summarizes and discusses fermentative and kinetic parameters from the state of the art of ethanol production by S. passalidarum in synthetic medium and hemicellulosic hydrolysates. Additionally, S. passalidarum performance for xylose consumption and ethanol production are discussed in comparison with other wild yeasts and genetically modified Saccharomyces cerevisiae. In addition to ethanol, the production of other chemical blocks such as xylitol, glycerol, acetoin, and 2,3-butanediol are also discussed, elucidating the potential of S. passalidarum for application in biorefineries. The potential of S. passalidarum for studies of mutagenesis, evolutionary, and genetic modifications is also reviewed in this work.

Unraveling continuous 2G ethanol production from xylose using hemicellulose hydrolysate and immobilized superior recombinant yeast in fixed-bed bioreactor

Development of a robust and competitive process for second generation (2G) ethanol production requires efficient fermentation of both glucose and xylose fractions generated after biomass pretreatment and saccharification, using industrial media containing high sugars concentration and inhibitors, under prolonged exposure to high ethanol titers. Thus, it is important to study the influence of these industrial operation conditions on yeast fermentation performance, which has been little addressed in the literature. In this work we evaluated the steady-state stability of continuous 2G ethanol production from xylose in a fixed bed reactor. The bioreactor was packed with recombinant, xylose-utilizing Saccharomyces cerevisiae cells entrapped in calcium alginate and it was operated with different inlet xylose concentrations and dilution rates. Medium supplementation with nutrients and scheduled washing steps were effective in maintaining high xylose conversion levels during continuous fermentation for more than 15 days with an ethanol productivity of 5.0 g/L.h. Effects of prolonged exposure to ethanol and inhibitors present in undetoxified hydrolysate were further investigated in repeated batches. Overall, the results show that improved ethanol tolerance in recombinant yeasts and innovative solutions to increase sugar concentration in the hydrolysates are the main challenges to achieve a feasible industrial process for 2 G ethanol production.

Novel potential yeast strains for the biotechnological production of xylitol from sugarcane bagasse

AbstractThis study aimed to screen the xylitol‐producing strains of Cyberlindnera xylosilytica and Wickerhamomyces rabaulensis for the bioconversion of the hemicellulosic fraction of sugarcane bagasse. Among the 16 strains tested, two of each species (C. xylosilytica UFMG‐CM‐Y309 and UFMG‐CM‐Y409, and W. rabaulensis UFMG‐CM‐Y3716 and UFMG‐CM‐Y3747) were selected on the basis of xylitol yield (Yp/s) and xylitol volumetric productivity (Qp) in YPX broth (yeast extract, 10 g L−1; peptone, 20 g L−1; and d‐xylose, 60 g L−1). These strains were cultivated in sugarcane bagasse hemicellulosic hydrolysate (SCHH) supplemented with ammonium sulfate, rice bran extract, and yeast extract. The xylitol yield was the highest in the strain C. xylosilytica UFMG‐CM‐Y‐309 with a production of 14.06 g L−1; xylitol yield, 0.63 g g−1; xylitol volumetric productivity, 0.20 g L−1 h−1. Xylitol yields ranged from 14% to 74% above those of other xylitol‐production yeast species. This work demonstrates the potential of biotechnological application of these yeasts for xylitol production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Mechanism study of novel inducer combinations containing laver powder for Penicillium piceum lignocellulolytic enzyme production

AbstractInducers play an important role in fungus cellulase production. In this study, a combination of Avicel and laver powder, which contains cellulose, hemicellulose, other polysaccharides, and crude lipid, was used to induce lignocellulolytic enzyme production in Penicillium piceum H16. When Avicel was supplemented with various amounts of laver powder, cellulase activities or extracellular protein yields increased by 11.4%–102.5%, relative to those observed when Avicel alone was used. In particular, filter paper and cellobiohydrolase activities increased by as much as 39.3% and 102.5%, respectively, after supplementation with laver powder. Furthermore, laver powder supplementation enhanced the efficiency of cellulose and hemicellulose hydrolysis in crude corn stover by 39.3% and 22.2%, respectively. The results suggest that laver powder and Avicel synergistically induce lignocellulytic enzyme production and P. piceum H16 growth. iTRAQ‐based quantitative proteomics analysis results further demonstrate that laver powder supplementation optimized the synergistic lignocellulytic enzyme cocktail from P. piceum H16 by upregulating the production of cellulase‐enhancing factors and lignocellulolytic enzymes. The oligosaccharides released by laver powder may account for the synergistic induction, which may help reduce the cost of producing lignocellulytic enzymes by filamentous fungi.

Optimization and empirical modelling of physical ‎properties of hydrothermally treated ‎oil ‎palm wood in ‎different ‎buffered media using ‎response ‎surface ‎methodology

Physical properties are one of the ‎drawbacks of oil palm wood ‎‎(OPW) and they need to ‎be ‎improved via an appropriate method. The ‎response surface methodology (RSM) based on central composite ‎design (CCD) was used to evaluate and optimize the parameters of a hydrothermal treatment ‎and to create an ‎empirical model of the mass loss (ML, %), equilibrium moisture ‎content ‎‎(EMC, %), and anti-swelling efficiency (ASE24h, %)‎‏ ‏responses‎. This ‎study focused on the ‎effect of ‎hydrothermal treatment (HTT) ‎in ‎buffer solutions to control the ‎destructive effects of ‎released ‎acids ‎caused by the degradation of ‎hemicellulose acetyl groups‏.‏‎ A CCD, as ‎the most common RSM design, was applied with three treatment factors including the ‎buffer solutions ‎‎(acidic, neutral, ‎and alkaline with pH of 5 to 8), temperature (80 to 140 ‎‎°С), ‎time (40 to ‎‎‎120 ‎min), and a total of 20 ‎experiments‎.‎‏ ‏‎The results ‎showed that the ‎effect of the treatment temperature ‎was more notable ‎than time. The medium acidity (pH) variations in HTT can lead ‎to ‎the removal of ‎extractives and starch, hemicelluloses ‎hydrolysis‎, ‎the ‎destruction of the parenchymal cells wall, and ‎weight loss. Based on the variance analysis, the ‎quadratic and linear models proved to be highly significant with ‎minimal probability values (< 0.0001). The optimum conditions ‎predicted for the HTT were a pH of 7.3, a temperature of ‎112.7 ‎°С, and ‎a‏ ‏time of ‎109.6 ‎min.

Obtaining hemicellulosic hydrolysate from sugarcane bagasse for microbial oil production by Lipomyces starkeyi.

The extraction of the hemicellulose fraction of sugarcane bagasse (SCB) by acid hydrolysis was evaluated in an autoclave and a Parr reactor aiming the application of the hydrolysate as a carbon source for lipid production by Lipomyces starkeyi. The hydrolysis that resulted in the highest sugar concentration was obtained by treatment in the Parr reactor (HHR) at 1.5% (m/v) H2SO4 and 120°C for 20min, reaching a hemicellulose conversion of approximately 82%. The adaptation of the yeast to the hydrolysate provided good fermentability and no lag phase. The fermentation of hemicellulose-derived sugars (HHR) by L. starkeyi resulted in a 27.8% (w/w) lipid content and YP/S of 0.16g/l.h. Increasing the inoculum size increased the lipid content by approximately 61%, reaching 44.8% (w/w). The hemicellulose hydrolysate from SCB is a potential substrate for L. starkeyi to produce lipids for biodiesel synthesis based on the biorefinery concept.

Enhanced glucose production from cellulose and corn stover hydrolysis by molten salt hydrates pretreatment

Molten salt hydrates (MSHs) are remarkable in breaking through the recalcitrant structure of microcrystalline cellulose and raw biomass. After being pretreated in 60 wt% LiBr at 130 °C for 2 h, cellulose crystallinity as well as degree of polymerization (DP) decreased. It was found that 91.3% yield of pretreated cellulose was removed from MSHs by filteration followed by being hydrolyzed into glucose with a high yield of 75.3% by dilute acid under mild reaction conditions. The pretreatment process also works on raw corn stover hydrolysis. After being pretreated at 100 °C for 5 h, 88.4% yield of cellulose in biomass was recovered and can be hydrolyzed into 54.9% yield of glucose with dilute acid. It was found that the cellulose in corn stover can be easier degraded compared with microcrystalline cellulose during MSHs pretreatment, which dues to the formation of acetic acid from hemicellulose hydrolysis. The proposed pretreatment technique presents a promising potential for glucose production from biomass in a commercial way.

Upgrading steam pretreatment by converting water-soluble carbohydrates into lactic acid prior to pretreatment

Steam pretreatment is an effective approach to open up the intact lignocellulosic matrix for biofuels and animal feed production. However, crop residues especially corn stover contain certain amounts of water-soluble carbohydrates (WSC), which are easily degraded into toxic 5-hydroxymethylfurfural (HMF) at high temperature and bring negative effects on subsequent utilization of lignocellulose biomass. Few studies have focused on the WSC loss and proposed a corresponding solution to utilize them in steam pretreatment. This study introduced a solid-state fermentation prior to steam pretreatment of corn stover to convert WSC into lactic acid, which could catalyze the hydrolysis of hemicellulose and acetyl groups in pretreatment. Compared to the regular steam pretreatment at the same severity (180 °C for 5 min), the conversion yields of xylan and arabinan in the steam pretreatment were both increased from 9.6% and 37.2% to 28.8% and 69.6%, respectively. Cellulose conversion also increased from 48.1% to 50.7% in the subsequent enzymatic hydrolysis. On the other hand, the generation of the toxic HMF reduced by 42.1% due to the pre-conversion of WSC into the relatively thermal stable lactic acid. This study provided an effective approach to process corn stover with higher hydrolysis yield and lower inhibitor generation.

Coculture with hemicellulose-fermenting microbes reverses inhibition of corn fiber solubilization by Clostridium thermocellum at elevated solids loadings

BackgroundThe cellulolytic thermophile Clostridium thermocellum is an important biocatalyst due to its ability to solubilize lignocellulosic feedstocks without the need for pretreatment or exogenous enzyme addition. At low concentrations of substrate, C. thermocellum can solubilize corn fiber > 95% in 5 days, but solubilization declines markedly at substrate concentrations higher than 20 g/L. This differs for model cellulose like Avicel, on which the maximum solubilization rate increases in proportion to substrate concentration. The goal of this study was to examine fermentation at increasing corn fiber concentrations and investigate possible reasons for declining performance.ResultsThe rate of growth of C. thermocellum on corn fiber, inferred from CipA scaffoldin levels measured by LC–MS/MS, showed very little increase with increasing solids loading. To test for inhibition, we evaluated the effects of spent broth on growth and cellulase activity. The liquids remaining after corn fiber fermentation were found to be strongly inhibitory to growth on cellobiose, a substrate that does not require cellulose hydrolysis. Additionally, the hydrolytic activity of C. thermocellum cellulase was also reduced to less-than half by adding spent broth. Noting that > 15 g/L hemicellulose oligosaccharides accumulated in the spent broth of a 40 g/L corn fiber fermentation, we tested the effect of various model carbohydrates on growth on cellobiose and Avicel. Some compounds like xylooligosaccharides caused a decline in cellulolytic activity and a reduction in the maximum solubilization rate on Avicel. However, there were no relevant model compounds that could replicate the strong inhibition by spent broth on C. thermocellum growth on cellobiose. Cocultures of C. thermocellum with hemicellulose-consuming partners—Herbinix spp. strain LL1355 and Thermoanaerobacterium thermosaccharolyticum—exhibited lower levels of unfermented hemicellulose hydrolysis products, a doubling of the maximum solubilization rate, and final solubilization increased from 67 to 93%.ConclusionsThis study documents inhibition of C. thermocellum with increasing corn fiber concentration and demonstrates inhibition of cellulase activity by xylooligosaccharides, but further work is needed to understand why growth on cellobiose was inhibited by corn fiber fermentation broth. Our results support the importance of hemicellulose-utilizing coculture partners to augment C. thermocellum in the fermentation of lignocellulosic feedstocks at high solids loading.

Effect of the Sugarcane Bagasse Deacetylation in the Pentoses Fermentation Process

Biomass alkaline deacetylation prior to acid pretreatment can be a promising alternative to reduce the toxicity of hemicellulosic hydrolysates and improve second-generation bioethanol production. In this paper, the effect of alkaline deacetylation of sugarcane bagasse on bioethanol production by Spathaspora passalidarum was evaluated. Sugarcane bagasse deacetylated hemicellulosic hydrolysate (DHH) was processed using the following sequence: (1) deacetylation (0.4%, w/v NaOH, 70 °C, 3 h) and (2) acid pretreatment (0.5% (v/v) of H2SO4, 140 °C, 15 min). Non-deacetylated, hemicellulosic hydrolysate (HH), was obtained applying only acid pretreatment (0.5% (v/v) of H2SO4, 140 °C, 15 min). Biomass deacetylation reduced the content of acetic acid and some phenolic compounds in the hydrolysate (DHH) compared to acid pretreatment (HH), which resulted in its low toxicity. Thus, the bioethanol production with DHH was of 16.92 g L−1, whereas only 1.3 g L−1 of bioethanol was obtained with HH fermentation. Deacetylation process provided a 13-fold increase in bioethanol production by S. passalidarum, showing that alkaline deacetylation followed by sulfuric acid pretreatment is a promising strategy to increase bioethanol production. This procedure provided a simple and practical alternative to the classic methods of detoxification of hemicellulosic hydrolysate from sugarcane bagasse.

Prospective evaluation of xylitol production using Dabaryomyces hansenii var hansenii, Pachysolen tannophilus, and Candida guillermondii with sustainable agricultural residues

In this study, agro-wastes, including corncob, rice straw, and wheat straw, were used as substrate for xylitol production using Dabaryomyces hansenii var hansenii, Pachysolen tannophilus, and Candida guillermondii. The experiments were performed using batch fermentation using hemicellulose hydrolyzate as substrate under optimum levels of the screened significant nutrients and process variables. Screening and optimization were carried out for all the systems using statistical methods based on experimental designs. Kinetics and modeling for xylitol production were developed using the logistic model for microbial growth, substrate utilization kinetics for the substrate utilization, and Luedeking-Piret model for the product formation. The model parameters were compared for all xylitol production carried out using pretreated hemicellulose hydrolyzates from corncob, rice straw, and wheat straw. Experimental analysis and modeling results revealed a maximum xylitol yield when corncob was hydrolyzed with Pachysolen tannophilus.

Nanofiltration of Organosolv Hemicellulose Hydrolyzate: Influence of Hydrothermal Pretreatment and Membrane Characteristics on Filtration Performance and Fouling

Xylose from hemicellulose hydrolyzates (HH) offers good prospects for valorization since it can be converted into a variety of high value-added products if it is separated and purified from the side streams of pulping. The influence of hydrothermal pretreatment of organosolv HH from beechwood pulping on the separation of xylose by four nanofiltration membranes was investigated. At first, a hydrothermal process was developed using response surface methodology to study appropriate process parameters (temperature and residence time) for maximum conversion of hemicellulose to xylose. Then, the nanofiltration process using a model solution, HH, and hydrothermally treated HH was assessed by an extensive performance and fouling analysis. Atomic force microscopy and physisorption analysis were applied to characterize the membranes NF (Alfa Laval), DK (GE Osmonics), TS40 (TriSep), and NF90 (DOW). Hydrothermal conversion at 180 °C and 3.1 min led to a conversion of almost 100% of hemicellulose to xylose without further degradation to chemical successors. The hydrothermal pretreatment of HH had positive effects on membrane performance and reduces fouling. Membrane characteristics such as lower surface roughness, a larger pore width and specific surface area, and smaller contact angles favored a higher flux and the ability to separate inhibitors as well as reduced fouling. Alkaline cleaning with P3-Ultrasil-53 was sufficient to remove the foulants and maintain a stable pure water flux.

Polyunsaturated fatty acids production by solid‐state fermentation on polyurethane foam by Mortierella alpina

Polyunsaturated fatty acids (PUFAs) are essential in healthy diets and their production is extremely important. Natural sources of PUFAs includes animal and aquatic products such as marine fish oil, however there are several limitations such as the decrease of fish stocks throughout the world. Thus, microbial oils are a preferable source of PUFAs. Herein, it was studied the production of PUFAs by Mortierella alpina under solid-state fermentation (SSF) using polyurethane foam as inert substrate and synthetic medium or lignocellulosic hydrolysate as source of C, N, and other nutrients. Several parameters of fermentation conditions were evaluated as carbon source, inductors addition, ratio C/N and temperature. The highest amount of total PUFAs per mass of solid (535.41 ± 24.12 mg/g), linoleic acid (129.66 ± 5.84 mg/g), and α-linoleic acid (401.93 ± 18.10mg/g) were produced when the culture medium contained 20 g/L glucose, 10% (w/v) linseed oil, the C/N ratio was adjusted to 25 and the incubation temperature was 25°C for 3 days decreasing to 16°C on the remaining 4 days of fermentation. In addition, a hemicellulosic hydrolysate can be used as low-cost substrate to produce PUFAs, although the production was lower than the achieved with synthetic medium. SSF showed an interesting technology for microbial PUFAs production.

Development of a purification process via crystallization of xylitol produced for bioprocess using a hemicellulosic hydrolysate from the cashew apple bagasse as feedstock.

Xylitol was biotechnologically produced by Kluyveromyces marxianus ATCC36907 using the hemicellulosic hydrolysate ofthe cashew apple bagasse (CABHH). Sequentially, the present study investigated the recovery and purification of xylitol evaluating different antisolvents [ethanol, isopropanol and the ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA)], their proportion in the medium (10-90% v/v), and their cooling rate (VC 0.25-0.50°C/min). These processes were contrasted with the crystallization process of commercial xylitol. This study is the first to assess xylitol crystallization using a protic ionic liquid. The hydrolysate obtained from a mild treatment with sulfuric acid contained mainly glucose and xylose at concentrations of 15.7g/L and 11.9g/L, respectively. With this bioprocess, a maximum xylitol production of 4.5g/L was achieved. The performance of the investigated antisolvents was similar in all conditions evaluated in the crystallization process of the commercial xylitol, with no significant difference in yields. For the crystallization processes of the produced xylitol, the best conditions were: 50% (v/v) isopropanol as antisolvent, cooling rate of 0.5°C/min, with a secondary nucleation of yield and purity of 69.7% and 84.8%, respectively. Under the same linear cooling rate, using ethanol, isopropanol or the protic ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA), crystallization did not occur, probably due to the presence of carbohydrates not metabolized by the yeast in the broth, which influences the solubility curve of xylitol. With the results of this work, a possible economical and environmentally friendly process of recovery and purification of xylitol from CABHH could be proposed.

Hydrogen production by Enterobacter sp. LBTM 2 using sugarcane bagasse hemicellulose hydrolysate and a synthetic substrate: understanding and controlling toxicity

Abstract Sugars released by thermochemical pretreatment of lignocellulosic biomass are possible substrate for hydrogen production. However, the major drawback for bacterial fermentation is the toxicity of weak acids and furan derivatives normally present in such substrate. This study aimed to investigate the metabolism involved in hydrogen production by the isolate Enterobacter LBTM2 using 10, 20 and 30-fold diluted synthetic (SH) and sugarcane bagasse hemicellulose (SBH) hydrolysates. In addition, the effects of acetic acid, formic acid and furfural on the bacterial metabolism, as well as detoxification of SBH with activated carbon and molecularly imprinted polymers on the hydrogen production were assessed. The results showed the best hydrogen yield was 0.46 mmol H2/mmol sugar for 20-times diluted SH, which was 2.3-times higher than obtained in SBH experiments. Bacterial growth and hydrogen production were negatively affected by 0.8 g/L of acetic acid when added alone, but were totally inhibited when formic acid (0.4 g/L) and furfural (0.3 g/L) were also supplied. However the maximum hydrogen production of SBH20 has duplicated when 3% of powdered activated carbon was added to the SBH experiment. The results presented herein can be helpful in understanding the bottlenecks in biohydrogen production and could contribute towards development of lignocellulosic biorefinery.

Production and Characterization of Thermoalkaliphilic Xylanase from Bacillus halodurans Cm1, and Its Application on Degumming Process of Ramie (Boehmeria nivea L.Gaud) Fiber as Textile Raw Material

Ramie fiber is a potential raw material to substitute imported raw materials such as cotton. Due to its higher hemicellulose content, ramie fiber required hydrolysis in a process called degumming. Enzymatic degumming is environmentally friendly compared to traditional process which using chemicals. Alkalithermophilic xylanase have high ability in hemicellulose hydrolysis. The production of xylanase was conducted by submerged fermentation of Bacillus halodurans CM1 in 20L bioreactor using Mamo and corncob medium with optimum conditions at 50°C, pH 9, 150 RPM and 1 vvm. The optimum specific activity of xylanase measured by Bailey method at 70°C and pH 9 is 475.41 U/mg. Xylanase was stable at 50°C, pH 9 and relatively stable to K+, Na2+, Co2+ and Ca2+ metal ions and Triton-X, Saba dan Tween-80 surfactants. Degumming process was carried out by immersing ramie fibers in formulated degumming solution with vlot 1:20 at 50°C, 150 RPM and 180 minutes. The enzymatic degumming process may substitute or reduce the use of chemicals due to its significant effect on ramie fiber quality. Enzymatic and chemical degumming process reduce the weight of Ramie Fiber to 7.23 %, and 7.72 %, slightly higher than enzymatic degumming 7.15%. Enzymatic degumming maintains tensile strength at 27.51 %. Whiteness index enhanced to 2.99% enzymatically and 3.49% chemically.
 Keywords: Bacillus halodurans CM1, enzymatic degumming, ramie fiber, textile industry, thermoalkaliphilic xylanase