Abstract: As biorefineries replace oil refineries, society and the environment will benefit from a switch from hydrocarbon feedstocks to renewable carbohydrates as a source of energy, materials and chemicals. Biomass-based ethanol technologies are rapidly evolving and bottlenecks are being identified that need to be overcome to achieve widespread commercialization. Current research is driven by the need to reduce the cost of biomass-ethanol production. The preferred method is to thermochemically pretreat the biomass material and subsequently, enzymatically hydrolyze the pretreated material to fermentable sugars that can then be converted to ethanol. Pretreatment research is focused on developing processes that would result in reduced bioconversion time, lower cellulase enzyme usage, and/or higher ethanol yields. Cellulase research efforts are focused on develop ing a cost-effective, highly thermostable, synergistically acting enzyme mixture that would meet the end user's needs. Robust fermentation microorganisms are also being developed for conversion of biomass sugars to ethanol and other bioproducts. An integrated research and development approach is paying off and commercial plants for the production of biomass-ethanol are close to becoming a reality.

Abstract: Most bacteria and their enzymes are destroyed or inactivated in the presence of organic solvents. Organic solvent tolerant bacteria are a relatively novel group of extremophilic microorganisms that combat these destructive effects and thrive in the presence of high concentrations of organic solvents as a result of various adaptations. These bacteria are being explored for their potential in industrial and environmental biotechnology, since their enzymes retain activity in the presence of toxic solvents. This property could be exploited to carry out bioremediation and biocatalysis in the presence of an organic phase. Because a large number of substrates used in industrial chemistry, such as steroids, are water-insoluble, their bioconversion rates are affected by poor dissolution in water. This problem can be overcome by carrying out the process in a biphasic organic-aqueous fermentation system, wherein the substrate is dissolved in the organic phase and provided to cells present in the aqueous phase. In bioprocessing of fine chemicals such as cis-diols and epoxides using such cultures, organic solvents can be used to extract a toxic product from the aqueous phase, thereby improving the efficiency of the process. Bacterial strains reported to grow on and utilize saturated concentrations of organic solvents such as toluene can revolutionize the removal of such pollutants. It is now known that enzymes display striking new properties in the presence of organic solvents. The role of solvent-stable enzymes in nonaqueous biocatalysis needs to be explored and could result in novel applications.

Abstract: Previous optimization strategies for the bioconversion of lignocellulosics by steam explosion technologies have focused on the effects of temperature, pH, and treatment time, but have not accounted for changes in severity brought about by properties inherent in the starting feedstock. Consequently, this study evaluated the effects of chip properties, feedstock size (40-mesh, 1.5 × 1.5 cm, 5 × 5 cm), and moisture content (12% and 30%) on the overall bioconversion process, and more specifically on the efficacy of removal of recalcitrant lignin from the lignocellulosic substrates following steam explosion. Increasing chip size resulted in an improvement in the solids recovery, with concurrent increases in the water soluble, hemicellulose-derived sugar recovery (7.5%). This increased recovery is a result of a decrease in the “relative severity” of the pretreatment as chip size increases. Additionally, the decreased relative severity minimized the condensation of the recalcitrant residual lignin and therefore increased the efficacy of peroxide fractionation, where a 60% improvement in lignin removal was possible with chips of larger initial size. Similarly, increased initial moisture content reduced the relative severity of the pretreatment, generating improved solids and hemicellulose-derived carbohydrate recovery. Both increased chip size and higher initial moisture content results in a substrate that performs better during peroxide delignification, and consequently enzymatic hydrolysis. Furthermore, a post steam-explosion refining step increased hemicellulose-derived sugar recovery and was most effectively delignified (to as low as 6.5%). The refined substrate could be enzymatically hydrolyzed to very high levels (98%) and relatively fast rates (1.23 g/L/h). © 2004 Wiley Periodicals, Inc.

Abstract: Fava beans are a rich source of levo-dihydroxy phenylalanine ( l -DOPA) the precursor of dopamine, and are being investigated for use in the management of Parkinson's disease. The present research was conducted to enrich the fava bean substrate with phenolic antioxidants and l -DOPA via solid-state bioconversion system using the food grade fungus Rhizopus oligosporus . The l -DOPA content in the fungal-grown fava bean increased significantly to approximately twice that of control, accompanied by moderate phenolic-linked antioxidant activity and higher fungal superoxide dismutase activity during early stages of growth. This indicated that l -DOPA can be mobilized and formed from fava bean substrates by fungal bioconversion and is contributed to the antioxidant functionality of such extracts. A high superoxide dismutase (SOD) activity during early and late growth stages indicates the likely oxidation stress of initial fungal colonization and later due to nutrient depletion. High levels of soluble phenolics were observed during late growth stages. During the course of solid-state growth there was an increase in β-glucosidase activity, which correlated to an increase in total phenolic content during the late stages. This suggests that the enzyme may play an important role in the release of phenolic aglycones from fava bean substrate and thereby increases the phenolic content and accompanying antioxidant activity. The implication from this study is that solid-state bioconversion of fava bean by R. oligosporus can significantly improve the phenolic antioxidant activity and Parkinson's relevant l -DOPA content.

Abstract: A readily fermentable pentose-containing hydrolysate was obtained from Brewery's spent grain by a two-step process consisting of an auto-hydrolysis (converting the hemicelluloses into oligosaccharides) followed by an enzymatic or sulfuric acid-catalyzed posthydrolysis (converting the oligosaccharides into monosaccharides). Enzymatic hydrolyses were performed with several commercial enzymes with xylanolytic and cellulolytic activities. Acid-catalyzed hydrolyses were carried out at 121°C under various sulfuric acid concentrations and reaction times, and the effects of treatments were interpreted by means of a corrected combined severity factor (CS 1), which varied in the range of 0.80–2.01. Under the tested conditions, chemicalhydrolysis allowed higher pentose yields than enzymatic hydrolysis. Optimized conditions (defined by CS 1=1.10) allowed both complete monosaccharide recovery and low content of inhibitors. Liquors subjected to posthydrolysis under optimal conditions were easily fermented by Debaryomyces hansenii CCMI 941 in semiaerobic shake-flask experiments, leading to xylitol and arabitol as major fermentation products. The bioconversion process was improved by hydrolysate concentration and supplementation of fermentation media with casamino acids.

Abstract: Food waste in the waste stream is becoming an important aspect of integrated waste management systems. Current efforts are composting and animal feeding. However, these food waste disposal practices rely on slow thermodynamic processes of composting or finding farmers with domestic animals capable of consuming the food wastes. Bioconversion, a potential alternative, is a waste management practice that converts food waste to insect larval biomass and organic residue. This project uses a native and common non-pest insect in Texas, the black soldier fly, which processes large quantities of food wastes, as well as animal wastes and sewage in its larval stage. The goal of this research is to facilitate the identification and development of the practical parameters of bioconversion methods at a large cafeteria. Three major factors were selected to evaluate the practicality of a bioconversion system: (1) the biological constraints on the species; (2) the economic costs and benefits for the local community; (3) the perception of and interaction between the public and management agencies with respect to the bioconversion process. Results indicate that bioconversion is feasible on all levels. Larvae tolerate and consume food waste as well as used cooking grease, reducing the overall waste volume by 30-70% in a series of experiments, with an average reduction of 50%. The economical benefits are reduced collection costs and profit from the sale of pupae as a feedstuff, which could amount to as much as $1,200 per month under optimal conditions. Social acceptance is possible, but requires education of the public, specifically targeting school children. Potential impediments to social acceptance include historical attitudes and ignorance, which could be overcome through effective educational efforts.

Abstract: A critical parameter affecting the economic feasibility of lignocellulosic bioconversion is the production of inexpensive and highly active cellulase enzymes in bulk quantity. A promising approach to reduce enzyme costs is to genetically transform plants with the genes of these enzymes, thereby producing the desired cellulases in the plants themselves. Extraction and recovery of active proteins or release of active cellulase from the plants during bioconversion could have a significant positive impact on overall lignocellulose conversion economics. The effects of ammonia fiber explosion (AFEX) pretreatment variables (treatment temperature, moisture content, and ammonia loading) on the activity of plant-produced heterologous cellulase enzyme were individually investigated via heat treatmett or ammonia treatment. Finally, we studied the effects of all these variables in concert through the AFEX process. The plant materials included transgenic tobacco plants expressing E1 (endoglucanase from Acidothermus cellulolyticus). The E1 activity was measured in untreated and AFEX-treated tobacco leaves to investigate the effects of the treatment on the activity of this enzyme. The maximum observed activity retention in AFEX-treated transgenic tobacco samples compared with untreated samples was approx 35% (at 60°C, 0.5∶1 ammonia loading, and 40% moisture). Based on these findings, it is our opinion that AFEX pretreatment is not a suitable option for releasing cellulase enzyme from transgenic plants.

Abstract: The conversion of xylose into xylitol by microorganisms (mainly yeasts) cultivated in hydrolysates obtained by diluted-acid hydrolysis of lignocellulosic materials has been extensively investigated. As the hydrolytic process generates a variety of toxic compounds that inhibit the xylose metabolism of the microorganisms (e.g. acetic acid, furfural, hydroxymethylfurfural and phenolic compounds), different detoxification methods have been used to remove these inhibitors from the hydrolysates, with a view to improving their fermentability and increasing the xylitol production. This paper reviews several studies dealing with some of these detoxification methods and also with the major factors in the xylose-xylitol bioconversion.

Abstract: This study was undertaken to screen the filamentous fungi isolated from its relevant habitats(wastewater, sewage sludge and sludge cake) for the bioconversion of domestic wastewater sludge. A total of 35 fungal strains were tested against wastewater sludge (total suspended solids, TSS 1%-5% w/w) to evaluate its potentiality for enhancing the biodegradability and dewaterability using liquid state bioconversion(LSB) process. The strains were divided into five groups i.e. Penicillium, Aspergillus, Trichoderma, Basidiomycete and Miscellaneous, respectively. The strains WWZP1003, SCahmA103, SCahmT105 and PC-9 among their respective groups of Penicillium, Aspergillus, Trichoderma and Basidiomycete played potential roles in terms of separation (formation of pellets/flocs/filaments), biodegradation(removal of COD) and filtration (filterability) of treated domestic wastewater sludge. The Miscellaneous group was not considered due to its unsatisfactory results as compared to the other groups. The pH value was also influenced by the microbial treatment during fermentation process. The filterability of treated sludge was improved by fungal treatment, and lowest filtration time was recorded for the strain WWZP1003 and SCahmA103 of Penicillium and Aspergillus groups respectively compared with other strains.

Abstract: Sorghum straw is a raw material useful for the xylose production by hydrolysis. The main application of xylose is its bioconversion to xylitol, a functional sweetener with important technological properties. The objective of this work was to study the hydrolysis of sorghum straw with hydrochloric acid at 100 C. Several concentrations of HCl (2–6%) and reaction time (0–300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentration of xylose, glucose, acetic acid and furfural in the hydrolysates were found and used to optimise the process and compared with results reported in the literature using other conditions and acids. Optimal conditions found for hydrolysis were 6% HCl at 100 C for 83 min, which yielded a solution with 21.3 g xylose/l, 4.7 g glucose/l, 0.8 g furfural/l and 2.8 g acetic acid/l. 2003 Elsevier Ltd. All rights reserved.

Abstract: Steam treatment of an industrial process stream, denoted starch-free wheat fiber, was investigated to improve the formation of monomeric sugars in subsequent enzymatic hydrolysis for further bioconversion into ethanol. The solid fraction in the process stream, derived from a combined starch and ethanol factory, was rich in arabinose (21.1%), xylose (30.1%), and glucose (18.6%), in the form of polysaccharides. Various conditions of steam pretreatment (170–220°C for 5–30 min) were evaluated, and their effect was assessed by enzymatic hydrolysis with 2 g of Celluclast + Ultraflo mixture/ 100 g of starch-free fiber (SFF) slurry at 5% dry matter (DM). The highest overall sugar yield for the combined steam pretreatment and enzymatic hydrolysis, 52 g /100 g of DM of SFF, corresponding to 74% of the theoretical, was achieved with pretreatment at 190°C for 10 min followed by enzymatic hydrolysis.

Abstract: The bioconversion of propionitrile to propionamide was catalysed by nitrile hydratase (NHase) using resting cells of Microbacterium imperiale CBS 498-74 (formerly, Brevibacterium imperiale). This microorganism, cultivated in a shake flask, at 28 °C, presented a specific NHase activity of 34.4 U mgDCW−1 (dry cell weight). The kinetic parameters, Km and Vmax, tested in 50 mM sodium phosphate buffer, pH 7.0, in the propionitrile bioconversion was evaluated in batch reactor at 10 °C and resulted 21.6 mM and 11.04 μmol min−1 mgDCW−1, respectively. The measured apparent activation energy, 25.54 kJ mol−1, indicated a partial control by mass transport, more likely through the cell wall. UF-membrane reactors were used for kinetic characterisation of the NHase catalysed reaction. The time dependence of enzyme deactivation on reaction temperature (from 5 to 25 °C), on substrate concentrations (from 100 to 800 mM), and on resting cell loading (from 1.5 to 200 μg DCW ml−1) indicated: lower diffusional control (Ea=37.73 kJ mol−1); and NHase irreversible damage caused by high substrate concentration. Finally, it is noteworthy that in an integral reactor continuously operating for 30 h, at 10 °C, 100% conversion of propionitrile (200 mM) was attained using 200 μg DCW ml−1 of resting cells, with a maximum volumetric productivity of 0.5 g l−1 h−1.

Abstract: Microbial degradation of geraniol, a natural monoterpene alcohol, was studied using a Rhodococcus sp. strain GR3 isolated from soil. The bioconversion product was identified as geranic acid [(2 E )-3,7-dimethylocta-2,6-dienoic acid] and its structure was established by (1)H-NMR, Fourier-transform IR spectrometry and GC-MS. The optimum temperature for this bioconversion was found to be 30 degrees C, and the reaction proceeds to a saturation with a time constant of 12.5 h. No appreciable degradation of product was observed using this bacterium.

Abstract: Hydrogen has been considered a potential fuel for the future since it is carbon-free and oxidized to water as a combustion product. Bioconversion of synthesis gas to hydrogen was demonstrated in a continuous fermentation utilizing malate as a carbon source. Rhodospirillum rubrum, an anaerobic photosynthetic bacterium catalyzed water gas shift reaction which was used in this research. The synthesis gas (CO) was used as a source of energy along with tungsten light supplied for growth and bioconversion of the photosynthetic bacteria. The microbial process in fermentation media was carried out in continuous culture to observe the effect of light intensity, agitation and liquid dilution rate on hydrogen production. The maximum hydrogen yield at 500 rpm was 0.65 mmol H2/mmol CO. Desired media flow rate was preferable for high hydrogen production. At 0.65 ml/min media, hydrogen was produced at 7.2 mmol/h. This new approach, use of biocatalyst, can be considered as an alternative method to the conventional Fischer Tropsch synthetic reactions, which were able to convert synthesis gas into hydrogen.

Abstract: The present work deals with a novel bioconversion of ferulate into vanillin using resting cells of Escherichia coli strain JM109/pBB1 as a biocatalyst. Biomass recycling from four successive bioconversion steps demonstrated the possibility of employing the proposed resting cell system for the continuous production of vanillin. Among the tested immobilization supports (polyurethane, synthetic sponge and porous glass) the synthetic sponge proved to be the best material in terms of both vanillin formation (C v = 0.080 g l -1 ) and productivity (Q v = 0.019 g I-1 h-1) at the end of entrapment tests. Thus, it was used in preliminary continuous tests using a fixed-bed column with immobilized E. coli JM109/pBB1 cells. The highest vanillin yield (Y P/S = 0.851 mol mol -1 ) was obtained at a dilution rate of 0.022 h -1 .