Abstract: Selected biodegradable municipal solid waste fractions were subjected to fifteen different pre-hydrolysis treatments to obtain the highest glucose yield for bio-ethanol production. Pre-hydrolysis treatments consisted of dilute acid (H(2)SO(4), HNO(3) or HCl, 1 and 4%, 180 min, 60 degrees C), steam treatment (121 and 134 degrees C, 15 min), microwave treatment (700 W, 2 min) or a combination of two of them. Enzymatic hydrolysis was carried out with Trichoderma reesei and Trichoderma viride (10 and 60 FPU g(-1) substrate). Glucose yields were compared using a factorial experimental design. The highest glucose yield (72.80%) was obtained with a pre-hydrolysis treatment consisting of H(2)SO(4) at 1% concentration, followed by steam treatment at 121 degrees C, and enzymatic hydrolysis with Trichoderma viride at 60 FPU g(-1) substrate. The contribution of enzyme loading and acid concentration was significantly higher (49.39 and 47.70%, respectively), than the contribution of temperature during steam treatment (0.13%) to the glucose yield.

Abstract: High vanillin productivity was achieved in the batch biotransformation of ferulic acid by Streptomyces sp. strain V-1. Due to the toxicity of vanillin and the product inhibition, fed-batch biotransformation with high concentration of ferulic acid was unsuccessful. To solve this problem and improve the vanillin yield, a biotransformation strategy using adsorbent resin was investigated. Several macroporous adsorbent resins were chosen to adsorb vanillin in situ during the bioconversion. Resin DM11 was found to be the best, which adsorbed the most vanillin and the least ferulic acid. When 8% resin DM11 (wet w/v) was added to the biotransformation system, 45 g l−1 ferulic acid could be added continually and 19.2 g l−1 vanillin was obtained within 55 h, which was the highest vanillin yield by bioconversion until now. This yield was remarkable for exceeding the crystallization concentration of vanillin and therefore had far-reaching consequence in its downstream processing.

Abstract: BACKGROUND: Crop residues as wheat straw are potential sources for fuel-ethanol production as an alternative to current production based on starch- or sugar-containing feedstocks. In this work, the effect of liquid hot water (LHW) process parameters, i.e. temperature (170 and 200 °C), residence time (0 and 40 min), solid concentration (5% and 10% (w/v)) and overpressure applied in the reactor (30 bar and no overpressure), on pretreatment of wheat straw was studied using a full factorial experimental design. Pretreatment effectiveness was evaluated based on the composition of the solid and liquid fractions obtained after filtration of pretreated material, and the susceptibility of the solid fraction to enzymatic hydrolysis (EH) using commercial cellulases. RESULTS: Statistical analysis showed that only temperature and time, within the limits of the experimental range, have a significant effect on the responses studied. While the effect of pretreatment time in hemicellulose-derived sugar recovery in prehydrolyzate depends on temperature, EH yield was enhanced as both temperature and time were increased. Maximum EH yield was 96 g glucose per 100 g potential glucose in pretreated residue. Xylan and acetyl groups content remaining in solid residue after pretretament, which were found to be directly correlated, had a marked effect on pretreated substrate degradability. CONCLUSIONS: LHW is an effective pretreatment to enhance the potential of wheat straw as substrate for ethanol production. Maximum hemicellulose-derived sugar recovery (53% of content in raw material) and EH yield (96% of theoretical) fall within different temperature and time intervals, suggesting separate optimization designs for these responses. Copyright © 2007 Society of Chemical Industry

Abstract: Background: Because ethanol organosolv pulping requires high pressure and is highly volatile, an atmospheric autocatalytic glycerol organosolv pretreatment process has been investigated. Enzymatic hydrolysis of wheat straw pretreated using this method was evaluated to explore a novel, economically competitive and environmentally friendly pretreatment technology for bioconversion of lignocellulosic biomass. The method also provides economical utilization of industrial glycerol, helping to cope with the challenge of the excess production of glycerol and to further defray the cost of biodiesel production. Results: With preliminary optimization of the parameters in the pretreatment process, pretreatment performed at 240 degrees C for 4 h with the glycerol addition of 15 g g(-1) dry feedstock and wash at 80 degrees C led to high recovery of cellulose (95%) and good removal of lignin (>70%), which formed, respectively, 80% and 10% of the pulp. The enzymatic hydrolysis of the pretreated wheat straw yielded 90% of theoretically achievable sugar after 24 h and 92% after 48 h. Conclusion: Atmospheric autocatalytic glycerol organosolv pretreatment removed significant amounts of hemicellulose and lignin without affecting good cellulose recovery. The proposed novel strategy increased the susceptible of wheat straw to enzyme attack and led to enzymatic hydrolysis that was comparable with that achieved using ethanol organosolv pretreatment. (C) 2007 Society of Chemical Industry

Abstract: Part I - Overview of Lignocelluloytic Biotechnology Part II - Lignocelluloytic Microorganisms and Enzymes Part III - Lignocellulose Bioconversion Part IV - Biotechnological Applications

Abstract: Dilute sulfuric acid pretreated corn stover is potential feedstock of industrial interest for second generation fuel ethanol production. However, the toxicity of corn stover hydrolysate (PCS) has been a challenge for fermentation by recombinant xylose fermenting organisms. In this work, the thermophilic anaerobic bacterial strain Thermoanaerobacter BG1L1 was assessed for its ability to ferment undetoxified PCS hydrolysate in a continuous immobilized reactor system at 70°C. The tested strain showed significant resistance to PCS, and substrate concentrations up to 15% total solids (TS) were fermented yielding ethanol of 0.39–0.42 g/g-sugars consumed. Xylose was nearly completely utilized (89–98%) for PCS up to 10% TS, whereas at 15% TS, xylose conversion was lowered to 67%. The reactor was operated continuously for 135 days, and no contamination was seen without the use of any agent for preventing bacterial infections. This study demonstrated that the use of immobilized thermophilic anaerobic bacteria for continuous ethanol fermentation could be promising in a commercial ethanol process in terms of system stability to process hardiness and reactor contamination. The tested microorganism has considerable potential to be a novel candidate for lignocellulose bioconversion into ethanol.

Abstract: Emerging markets for fuels and energy from crop biomass are creating new opportunities for redesigning agricultural systems for improved ecological function and energy-use effi ciency. Innovative bioconversion processes confi gured to recover key plant nutrients from biomass will allow recycling nutrients to crop fi elds, thereby closing nutrient cycles and reducing the energetic and economic costs of fertilization. Such advanced bioconversion matched with complementary biomass production may promote the development of highly productive agricultural– industrial systems that protect environmental quality. A generally representative example of nutrient recovery from an integrated biological and thermochemical conversion process designed to produce ethanol and synthetic fuels from switchgrass (Panicum virgatum L.) indicates that approximately 111 kg ha −1 yr −1 of N can be recovered. This is equivalent to 78% of the N-fertilizer input required. This example illustrates that N recovery and cycling could signifi cantly improve the sustainability of biomass production as well as the overall energy balance of ethanol production from lignocellulosic biomass. Demand for lignocellulosic biomass as an industrial feedstock may also allow the introduction of new crops and cropping systems. In addition to perennial grasses, double-crop sequences and systems incorporating greater use of legumes, cover crops, and living mulch may be able to produce large amounts of biomass while improving resource use effi ciency and reducing environmental impact.

Abstract: A variety of degradation products are produced upon pretreatment of lignocellulosic biomass with dilute acid. To date, the complexity of these samples has significantly limited the scope of efforts to perform summative analyses of degradation products. Qualitative and quantitative interrogation of hydrolysates is also paramount to identifying potential correlations between pretreatment chemistry and microbial inhibition in downstream bioconversion processes. A recently developed reversed-phase high performance liquid chromatography technique with UV detection has been applied to perform quantitative assessments of a variety of hydrolysate components as a function of pretreatment time and temperature. Correlations of product concentrations to the pretreatment severity function indicate differing responses of various compounds to the kinetic influences of temperature and reaction time. Of the compounds measured, four demonstrated initial accumulation rates were sufficiently linear over the time period tested to enable determination of activation energy E(a). All four compounds appear to demonstrate higher E(a) than that assumed in the commonly applied severity function. Overall accumulation trends for most compounds indicated similar under-estimation of apparent activation energy by the severity function. Biotechnol. Bioeng. 2007;98: 1135-1145. (c) 2007 Wiley Periodicals, Inc.

Abstract: Grass lignocelluloses are limited in bioconversion by aromatic constituents, which include both lignins and phenolic acids esters. Histochemistry, ultraviolet absorption microspectrophotometry, and response to microorganisms and specific enzymes have been used to determine the significance of aromatics toward recalcitrance. Coniferyl lignin appears to be the most effective limitation to biodegradation, existing in xylem cells of vascular tissues; cell walls with syringyl lignin, for example, leaf sclerenchyma, are less recalcitrant. Esterified phenolic acids, i.e., ferulic and p-coumaric acids, often constitute a major chemical limitation in nonlignified cell walls to biodegradation in grasses, especially warm-season species. Methods to improve biodegradation in grasses, especially warm-season species. Methods to improve biodegradability through modification of aromatics include: plant breeding, use of lignin-degrading white-rot fungi, and addition of esterases. Plant breeding for new cultivars has been especially effective for nutritionally improved forages, for example, bermudagrasses. In laboratory studies, selective white-rot fungi that lack cellulases delignified the lignocellulosic materials and improved fermentation of residual carbohydrates. Phenolic acid esterases released p-coumaric and ferulic acids for potential coproducts, improved the available sugars for fermentation, and improved biodegradation. The separation and removal of the aromatic components for coproducts, while enhancing the availability of sugars for bioconversion, could improve the economics of bioconversion.

Abstract: This article appraises the need for introducing appropriate technology to improve the production of renewable energy, particularly on the community basis and social aspect of sustainability. Using two-sequential steps of acid hydrolysis (10% sulfuric acid) and yeast (Candida shehatae; xylose-fermenting yeast) fermentation, bioconversion of water hyacinth (Eichhornia crassipes; a noxious weed and fast growing aquatic plant widely distributed in many tropical regions of the world) to liquid ethanol has successfully been performed. The maximum ethanol yield coefficient of 0.19 g g -1 WH with the productivity of 0.008 g l -1 h -1 was achieved. This is as well comparable to those obtained from the enzymatic saccharification and/or the fermentation of acid-pretreated water hyacinth hydrolysate using fully-equipped fermenter reported elsewhere. More importantly, determinations of xylose and ethanol contents can potentially be performed using two reliable colorimetric approaches (Phloroglucinol and Dichromate assays, respectively) in conjunction with home-made portable photometer. The technology presented herein can be transferred and implemented to gain opportunity of becoming self-reliance of community in the third world countries.

Abstract: This article appraises the need for introducing appropriate technology to improve the production of renewable energy, particularly on the community basis and social aspect of sustainability. Using two-sequential steps of acid hydrolysis (10% sulfuric acid) and yeast (Candida shehatae; xylose-fermenting yeast) fermentation, bioconversion of water hyacinth (Eichhornia crassipes; a noxious weed and fast growing aquatic plant widely distributed in many tropical regions of the world) to liquid ethanol has successfully been performed. The maximum ethanol yield coefficient of 0.19 g gWH with the productivity of 0.008 g l h was achieved. This is as well comparable to those obtained from the enzymatic saccharification and/or the fermentation of acid-pretreated water hyacinth hydrolysate using fully-equipped fermenter reported elsewhere. More importantly, determinations of xylose and ethanol contents can potentially be performed using two reliable colorimetric approaches (Phloroglucinol and Dichromate assays, respectively) in conjunction with home-made portable photometer. The technology presented herein can be transferred and implemented to gain opportunity of becoming self-reliance of community in the third world countries.

Abstract: Traditional thermophillic composting is commonly for treatment of sludge. A related technique as vermicomposting process, using earthworms to breakdown sludge, is also becoming popular. These two techniques have their inherent advantages and disadvantages. The combined approach suggested in this study to enhance the overall process and improve the products qualities. Two systems, vermicomposting and combined compost-vermicomposting processes, have been investigated in this study. The sludge used in this study was obtained from the drying beds of South Isfahan wastewater treatment plant. The sludge mixed with sawdust to provide C/N ratio of 25/1. Eisenia fetida was the species of earthworms used in the vermicomposting processes. The results obtained indicate reduction in the amount of volatile solids, total carbon and C/N ratio with the vermicompost age, which indicates the reduction in the biodegradable organic content and mineralization of sludge. Also increase in phosphorus concentration by the end process because of mineralization of organic matter. The results indicate that, a system that combines the two mentioned processes not only shortens stabilization time, but also improves the products quality. Combining the two systems resulted in a product that was more stable and homogenous; the product could meet the pathogen reduction requirements. © 2007 Asian Network for Scientific Information.

Abstract: The effect of glucose on xylose-to-xylitol bioconversion by Candida guilliermondii was examined by adding it to sugarcane bagasse hydrolysate medium to obtain different glucose:xylose ratios (1:25, 1:12, 1:5 and 1:2.5). Under experimental conditions, increasing glucose:xylose ratio improved the assimilation of the xylose present in the hydrolysate by yeast, resulting in biomass increase, and in the formation of xylitol and glycerol/ethanol by-products. Maximum values of xylitol yield (0.59 g g-1) and volumetric productivity (0.53 g l-1.h-1) were obtained with glucose:xylose ratio of 1:5, resulting in the higher conversion efficiency (64.3%).

Abstract: Hemicellulosic hydrolyzates from vineshoot trimmings obtained by dilute sulfuric acid hydrolysis were evaluated for xylitol production by Debaryomyces hansenii NRRL Y-7426. Bioconversion was not efficient, however, since a mixture of products (mainly ethanol) was achieved. Taking into account that hexoses (such as glucose or mannose) can inhibit xylose metabolism by repression and inactivation of the xylose transport system or catabolic enzymes and that these hemicellulosic hydrolyzates are characterized by a high glucose concentration, a novel technology was developed, sequentially transforming glucose into lactic acid by Lactobacillus rhamnosus followed by fermentation of xylose into xylitol by Debaryomyces hansenii after L. rhamnosus removal by microfiltration. Optimal conditions were achieved using detoxified concentrated hemicellulosic hydrolyzates, after CaCO3 addition in both stages of fermentation and using nitrogen purges after sampling in order to reduce the oxygen dissolved. Under these conditions 31.5 g lactic acid L−1 (QLA = 1.312 g L−1 h−1 and YLA/S = 0.93 g g−1) and 27.5 g xylitol L−1 (QXylitol = 0.458 g L−1 h−1 and YXylitol/S = 0.53 g g−1) were produced. Finally, lactic acid was selectively recovered using the resin Amberlite IRA 400 (0.0374 g of lactic acid g−1 of dry resin), allowing a further recovery of xylitol by sequential stages of adsorption, concentration, ethanol precipitation, concentration and crystallization to obtain food-grade xylitol according to a developed process. Copyright © 2007 Society of Chemical Industry

Abstract: The present research investigated the enrichment of fenugreek (Trigonella foenum graceum) seed substrate with phenolic antioxidants and L-DOPA via fungal-based solid-state bioconversion (SSB) system. This approach using food grade fungus Rhizopus oligosporus, was chosen because it has been demonstrated to be effective in other seed and food substrates for improving health-relevant functionality and has long history of use for food processing in Asia. The protein content and beta-glucosidase activity of the substrate which reflects fungal growth, increased with incubation time in conjunction with enhanced phenolic content and also suggested its possible involvement in phenolic mobilization. The antioxidant activity assayed by beta-carotene bleaching and DPPH free radical scavenging methods both indicated high activity during early growth stage (days 4-6) followed by reduced activity during later growth stage (days 8-20). A direct association between higher phenolic contents during early growth stage (days 4-6) and antioxidant activity suggested a link to mobilization of polymeric and hydrophobic phenolic forms. The L-DOPA content of the fenugreek extract fluctuated during the course of bioconversion with higher levels during days 6-10 (1.5-1.7 mg/g DW). The SSB process substantially improved the in vitro porcine alpha-amylase inhibition activity by 75 % on day 4 which correlated to higher levels of total phenolics and related antioxidant activity of the extracts. The high alpha-amylase inhibitory activity also coincided with high L-DOPA content on day 6. These results have implications for diet-based diabetes management. The same bioconversion stage had Helicobacter pylori inhibitory activity, which has implications for ulcer management.

Abstract: Transcriptome data for a xylitol-producing recombinant Escherichia coli were obtained and used to tune up its productivity. Structural genes of NADPH-dependent D-xylose reductase and D-xylose permease were inserted into an Escherichia coli chromosome to construct a recombinant strain producing xylitol from D-xylose for use as a model system for NADPH-dependent bioconversion. Transcriptome analysis of xylitol-producing and nonproducing conditions for the recombinant revealed that xylitol production down-regulated 56 genes. These genes were then selected as candidate factors for suppression of the NADPH supply and were disrupted to validate their functions. Of the gene disruptants, that resulting from the deletion of yhbC showed the best bioconversion rate. Also, the deletion accelerated cell growth during log phase. The features of the mutant could be maintained in jar fermenter-scale production of xylitol. Thus, our novel molecular host strain breeding method using transcriptome analysis was fully effective and could be applied to improving various industrial strains.

Abstract: Sugarcane bagasse pretreated by three different procedures (with 2% [v/v] polyethyleneimine (PEI), with 2% [w/v] NaOH, or with a sequence of NaOH and PEI) was used as cell immobilization carrier for xylitol production byCandida guilliermondii yeast. Fermentations using these pretreated carriers were performed in semidefined medium and in a hydrolysate medium produced from sugarcane bagasse hemicellulose. Sugarcane bagasse pretreated with NaOH was the best carrier obtained with respect to immobilization efficiency, because it was able to immobilize a major quantity of cells (0.30 g of cells/g of bagasse). Fermentation in semidefined medium using the NaOH-pretreated carrier attained a high efficiency of xylose-to-xylitol bioconversion (96% of the theoretical value). From hydrolysate medium, the bioconversion efficiency was lower (63%), probably owing to the presence of other substances in the medium that caused an inadequate mass transfer to the cells. In this fermentation medium, better results with relation to xylitol production were obtained by using PEI-pretreated carrier (xylose-to-xylitol bioconversion of 81% of the theoretical and volumetric productivity of 0.43 g/[L·h]). The results showed that sugarcane bagasse is a low-cost material with great potential for use as cell immobilization carrier in the fermentative process for xylitol production.

Abstract: Aims: To exploit conidiospores of Aspergillus niger as a vector for glucose oxidase extraction from solid media, and their direct use as biocatalyst in the bioconversion of glucose to gluconic acid. Methods and Results: Spores of A. niger (200 h old) were shown to fully retain all the glucose oxidase synthesized by the mycelium during solid-state fermentation (SSF). They acted as catalyst and carried out the bioconversion reaction effectively, provided they were permeabilized by freezing and thawing. Glucose oxidase activity was found retained in the spores even after repeated washings. Average rate of reaction was 1AE 5gl )1 h )1 with 102 g l )1 of gluconic acid produced out of 100 g l )1 glucose consumed after approx. 100 h reaction, which corresponded to a molar yield close to 93%. These results were obtained with permeabilized spores in the presence of a germination inhibitor, sodium azide. Conclusions: Spores of A. niger served as efficient catalyst in the model bioconversion reaction after permeabilization. Significance and Impact of the Study: To our knowledge, this is the first detailed study on the ability of A. niger spores to act as reservoir of enzyme synthesized during SSF without its release into solid media. Use of this material served as an innovative concept for enzyme extraction and purification from a solid medium. Moreover, this approach could compete efficiently with the conventional use of mycelial form of the fungus in gluconic acid production.

Abstract: A method, system, apparatus and program extracts energy from organic residual materials produced by the manufacturing of biofuels. Energy is extracted from the biofuels residuals using anaerobic bioconversion to produce a fuel for use in the manufacturing process for producing synthetic biofuel or as an additional energy product for sale comprises: providing at least one bioconversion tank for conversion of organic waste material, the bioconversion tank containing an active biomass comprising at least one bacteria that decomposes organic material; providing at least one inlet to the bioconversion for organic material; a processor that receives and stores information on: the status of chemical oxygen demand of the active biomass; and the oxygen provision capability of any organic material that can be fed into the bioconversion tank through an inlet; a mass flow control system controlled by the processor which feeds at least one organic material through an inlet at a rate based at least in part upon the status of chemical oxygen demand in the bioconversion tank as recognized by the processor.

Abstract: Methane production by anaerobic digestion of kelp is a relatively new approach to augmenting the national gas supply. Digestion of the giant marine kelp Macrocystis pyrifera, investigated in a series of bench-scale experiments at the Institute of Gas Technology (IGT), is reported. Conducted with both untreated and chemically pretreated plants, the tests have evaluated the effects of major limits on bioconversion of kelp, including temperature, indigenous salt concentration, external nutrients, inocula source, loading, residence time, manner of mixing and frequency of feeding. A detailed chemical characterisation of the kelp samples is presented. Raw-kelp digestion was not limited by nitrogen or phosphorus. Temperature ranges of 35–40°C and 50–55°C were found to be optimum for mesophilic and thermophilic digestion of raw kelp. The mesophilic methane yield in the semicontinuous mode was about 4.5 SCF/lb (280.94 cm3 g−1) of volatile solids (VS) added compared with a thermophilic methane yield of 2.4 SCF/lb (149.83 cm3 g−1) of VS added. The mesophilic organisms could be acclimatised to a salt concentration that has a conductivity of 43 000 μmho cm−1 without any deleterious effect. Thermophilic methanogens were more sensitive to high salt concentrations than the mesophilic organisms. Raw kelp had an estimated ultimate biodegradability of 80%. Mannitol and algin were the most biodegradable components.

Abstract: The influence of ultrasonication on hydrolysis, acidogenesis, and methanogenesis in anaerobic decomposition of sludge was investigated. The sonicated sludge exhibited prehydrolysis and preacidogenesis effects in the anaerobic decomposition process. First-order hydrolysis rates increased from 0.0384 day -1 in the control digester to 0.0672 day -1 in the digester fed, with sludge sonicated at 0.52 W/mL. The sonication appeared to be ineffective in relation to acidogenesis reaction rates, but it provided a better buffering capacity to diminish the adverse effect of acidification. Digesters fed with sonicated sludge demonstrated enhanced methanogenesis over the control unit. Determination by coenzyme F420 verified that sonication is able to promote the growth of methanogenic biomass and facilitate a positive methanogenic microbial development in suppressing the initial methanogenesis limitation. The results suggest that ultrasonication could enhance anaerobic decomposition of sludge, resulting in an accelerated bioconversion, improved organics degradation, improved biogas production, and increased methane content.

Abstract: incubated for 48 h at 30 o C. The enzymatic conversion of these agro-residues was carried out using immobilized tannase. Substrate concentrations of 8% sal seed, 7% myrobalan and 6% tea leaf (w/v) were found to be the optimum for maximum bioconversion. The maximum bioconversion (90 and 87%, respectively) was achieved with sal seed and tea leaf as substrate at 40 °C and initial pH 4.5. In case of myrobalan, the maximum bioconversion was 90.2% at 50 °C and initial pH 5.0. Moreover, optimization of the pH and temperature largely reduced the incubation time to 36 h. The immobilized tannase was stable for 7 cycles. The kinetic properties of immobilized enzyme revealed that there was a decrease in maximal reaction velocity (V max ) and increase in Michaelis constant (K m) when compared to its free native counterpart.

Abstract: Publisher Summary This chapter reviews the bioconversion of whey lactose into microbial exopolysaccharides (EPS). It also emphasizes challenges facing the fermentation process as well as the criteria to be considered to develop it into an effective and valuable bioconversion process. Microbial EPS such as xanthan gum and alginate continue to receive increasing applications in response to the demands for desirable product texture and enhanced processibility of nutritional and healthful food products. These polymers require simple sugars as building blocks and are produced via natural fermentation processes using specific microorganisms. The inherent specificity of the enzymes involved and the controllability of a bioprocess make bioconversion into EPS an ideal candidate for the effective utilization of whey lactose. Bioconversion is considered the most feasible means to effectively transform milk lactose from a low-value feedstock into value-added products. However, the direct fermentation of lactose by participating microorganisms usually suffers from a limited conversion rate as is found in yeast fermentation. The utilization of lactose as the building blocks for the synthesis of microbial EPS thus appears to be a favorable option. Microbial EPS already have many important applications in food, chemical, and pharmaceutical industries, and they continue to find new uses in emerging markets.