Abstract: Xylan is a polysaccharide located in the cell wall of higher plants which is one of the major components of lignocellulosic materials. In some higher plants and agricultural wastes the xylan is 20-40% of the dry material.' It consists of p-1, 4-linked D-xylose chain. The breakdown of hemicellulose is accomplished by the synergistic action of xylanase (1,4+-~-xylan xylanohydrolase, EC 3.2.1.8) and P-xylosidase (P-D-xyloside xylohydrolase, EC 3.2.1.37). Such enzymes are useful in the degradation of biomaterials containing hemicellulose for the production of monosaccharides from which single-cell protein, single-cell oil, or ethanol could be produced. '-I1 The production and properties of enzymes capable of breaking down cellulose have been extensively st~died. '~-~' Although there are reports on the production of xylanase,'8-26 the behavior of xylanases and its involvement in the utilization of complex lignocellulosic material is still incomplete. Therefore, the present communication deals with the utilization of some lignocellulosic materials by A . ochraceus for xylanase and pxylosidase production. The use of purified xylan enhances the cost of enzyme production and is a major limitation to the economic feasibility of bioconversion and utilization of lignocellulosic materials. Therefore, in this work, easily available substrates like wheat straw, wheat bran, and sugarcane bagasse were used in the experiment to obtain optimum levels of xylanases by the fungal strain A . ochruceus.

Abstract: alpha-Ionone, alpha-methylionone, and alpha-isomethylionone were converted by Aspergillus niger JTS 191. The individual bioconversion products from alpha-ionone were isolated and identified by spectrometry and organic synthesis. The major products were cis-3-hydroxy-alpha-ionone, trans-3-hydroxy-alpha-ionone, and 3-oxo-alpha-ionone. 2,3-Dehydro-alpha-ionone, 3,4-dehydro-beta-ionone, and 1-(6,6-dimethyl-2-methylene-3-cyclohexenyl)-buten-3-one were also identified. Analogous bioconversion products from alpha-methylionone and alpha-isomethylionone were also identified. From results of gas-liquid chromatographic analysis during the fermentation, we propose a metabolic pathway for alpha-ionones and elucidation of stereochemical features of the bioconversion.

Abstract: Coffee pulp is a greatly abundant agroindustrial waste with a limited use as feed. due to Us high contents oftoxic compounds such as caffeine. tarmines and polyphenols. An alternative to increase Us utilization could be a detoxification process through Sal1d State Fermentation. using filamentous fungi. These microorganisms are able to degrade caffeine when Uis used as nitrogen source. Same degradation pathways are known. and urea 1s one of the ultimate products of this degradation. Sail. leaves and coffee fruits samples was recolected from Xalapa. Ver. and Saconusco. Chis .. Mexico: the isolation was done by inoculating samples on 3 semisynthetic culture media contening coffee extract CA). coffee extract with sucrose (8) and coffee pulp extract (C) with mineral salts and streptomycine (30 ppm). Cultures were incubated at 25"C and 35"C. The purification was made through succesive repl1cation with the same isolation culture medium. In this form. 280 pure strains were isolated and identlfied by macroscoplc and microscopie observations on standard culture media plates and microculture. Subsequently. a physiologie study ofthese strains was made in l1quid medium with caffeine and other controled conditions. Strains were selected for their caffeine degradation capacity in this selective l1quid medium. After 70 hours of incubation. strains with nearly 80% of caffeine degradation were found and in sorne cases correlated with a notable increase in pH. Most of the isolated microorganisms were Aspergillus. Penicillium, Trichoderma and

Abstract: Enzymatic conversion of cellulosic wastes has great potential for the production of fuels and chemicals. However, the widespread conversion of cellulosic waste has been delayed by unfavorable process economics. The attrition bioreactor (ABR) combines wet ball milling and enzymatic hydrolysis in one process step. It was found that the ABR did not accelerate enzyme deactivation. Interfacial forces, not shear forces, caused the most deactivation. Elimination of the air-liquid interface by covering the reactor substantially increased enzyme stability. A simple exponential kinetic model was tested to predict the cellulose conversion in an ABR. Kinetic parameters were estimated from batch runs performed at various enzyme and substrate concentrations.

Abstract: Bioconversion of polymeric substrates in anaerobic digesters is slow. Exploratory research was conducted on the effects of the addition of soluble oxidants to a thermophilic, anaerobic, semicontinuous stirred tank reactor (CSTR) fed a biomass feedstock. After adaptation, added nitrate was quantitatively reduced to ammonia and isotopelabeling experiments confirmed that denitrification reactions did not occur. Addition of sulfate to a continuous nitrate amended digester resulted in sulfate accumulation, whereas sulfate addition to nonnitrate-amended digesters resulted in sulfate reduction. These results support the hypothesis that nitrate is preferentially reduced in the presence of sulfate and nitrate.

Abstract: The effects of pH, temperature and concentration of citrate were investigated to achieve an optimal production of diacetyl, acetoin and C2 compounds such as acetaldehyde, acetate and ethanol for free and immobilized cells. The critical conditions of culture, 22°C, pH 4.8, increased the production of C4 compounds (diacetyl, acetoin, 2, 3 butylene glycol), C2 compounds (acetaldehyde, ethanol, acetate) and formate. A higher yield of C2 and C4 compounds was observed for the immobilized cells than for the free cells in continuous culture. At 75 mMol/l of citrate, the citrate bioconversion yield was 42.8% and 80% for free and immobilized cells, respectively. This paper discusses citrate and lactose utilization and NADH2 part on diacetyl reduction.

Abstract: Bioconversions of lignocellulosic biomass, in particular sawdusts, into ethanol were investigated. First, acid hydrolyses by dilute sulfuric acids using 0.5, 1.0, and 2.0 weight percent were performed. The optimum hydrolysis condition was found to be 1% acid at 124C and hydrolysis time 50 min. The total yields of saccharification, primarily xylose, is 23.7 g which is obtained from 100 grams of sawdusts with a liter of dilute at the optimum condition. Second, fermentations of xylose into ethanol were investigated using Clostridium thermosaccharolyticum (ATCC 31925) by a batch reactor and by a continuous up-flow cylindrical reactor. In a continuous up-flow reactor, two modes of operation are studied; namely, cells immobilized on polystyrene chips (size 2.79 {times} 3.78 {times} 2.64 mm) and cells freely suspended in the flowing substrate stream. The flow rates investigated were 17.5, 29.5, and 51.2 ml/hr for immobilized case and 27.3, 42.2, 66.1, and 109 ml/hr for free suspension case. The maximum concentration of ethanol yield obtained from the initial concentration of 6 g/l xylose was 1.8 g/l by a batch reactor, which is equivalent 60% of the theoretical conversion of xylose by weight. If the dilution rate is less than 0.3 hr{sup {minus}1}, the concentration of ethanolmore » by the continuous up-flow reactor for both cases approach the maximum of that by a batch reactor. Modelings of bioconversion kinetic parameters in Monod and Luedeking-Piret formulas were also obtained. The specific growth rate for the microorganism in CM-4 medium is found to be 0.43 hr{sup {minus}1}.« less

Abstract: A new type of reactor, the attrition bioreactor, has been developed to increase the rate of the enzymatic hydrolysis of cellulose and also to cut pretreatment costs. It was found that the attrition bioreactor could be operated continuously or semicontinuously in conjunction with a membrane filter to produce a high cellulose conversion rate and low enzyme consumption. The membrane filter served to contain the enzyme and cellulose within the reactor while allowing sugar to permeate as a product.

Abstract: The invention provides a process for the microbial bioconversion of cereal milling by-products into proteinaceous material for human consumption. The by-products are aerobically fermented in a culture of the fungus Neurospora sitophila in the presence of suitable temperature, pH and nutrient conditions, for a time sufficient to grow microbial biomass protein.

Abstract: The production of citric acid by batch fermentation with the yeast strain Candida tropicalis ATCC 20240 was chosen as a potential process for the valorization of kraft black liquor. The effect of nitrogen concentration was studied and direct bioconversion of acetate to citrate was achieved when no nitrogen was supplemented to the medium. The use of kraft black liquor's acetate as a potential substrate for citric acid production was investigated. The acid precipitated liquor was highly inhibitory when its concentration was above 25% of the fermentation broth content. The yields of citric acid at low concentrations of kraft black liquor (5% and 15%) were the same as those recorded in synthetic acetate medium. Other organic acids present in the liquor may affect the yields and rates of citric acid production over acetate. Substrate uptake rates and product formation rates were lower, however, in comparison to synthetic media. The utilization of immobilized biomass improved the process parameters on kraft black liquor and enhanced the fermentation capabilities.

Abstract: A total of 19 microorganisms, selected from genera of bacteria, fungi and yeasts, were screened for their ability to hydrolyse isosorbide dinitrate (ISDN) to mononitrates. Cunninghamella echinulata and Cunninghamella elegans showed rates of bioconversion of ISDN of 74% and 88% respectively, measured after 73 h. However, the two strains exhibited opposite stereoselectivity, as reflected in the ratios of isosorbide 5-mononitrate (5-ISMN) to isosorbide 2-mononitrate (2-ISMN). These were 2.57 and 0.75 for C. echinulata and C. elegans, respectively.

Abstract: Strain RD330 a transposon mutant of Alcaligenes eutrophus JMP134 was considered to be dienelactone hydrolase defective (Don et al. 1985). During a bioconversion experiment with 3CB (3-chlorobenzoate) 2CMA (2-chloro-cis,cis-muconate) was accumulated by RD330 with an overall amount of 31%, but no dienelactone could be detected. Enzyme tests revealed that both enzymes 2CMA-cycloisomerase and dienelactone-hydrolase were induced at low levels in RD330 by 3CB and its metabolites. The control of 3CB addition during the bioconversion experiment was performed by on line HPLC (high pressure liquid chromatography).

Abstract: The purpose of this investigation is to determine the feasibility of bioprocessing municipal solid waste (MSW) to produce organic acids and recover the acids for hydrocarbon fuels production. This work has focused on acid production from anaerobic digestion of a simulated MSW material and a densified refuse-derived-fuels MSW substrate using 5-L continuously stirred and 12-L packed-bed anaerobic digesters. Methane generation was inhibited by heat treatment, addition of a methanogen-inhibiting compound, low pH, inoculum from a long-term acid-adapted culture, and short retention times. Steady-state operation was reached with acid concentrations of 15,000 to 18,000 mg/L. Nitrogen supplements to the feedstock increased volatile acid concentrations to between 27,000 and 30,000 mg/L. Extraction of digester fluids containing 15,000 mg/L total acids with trioctylphosphine oxide in heptane recovered more than 82% of the acid in a single extraction. Work continues on maximizing the acid production and recovery from anaerobically digested MSW substrate. 56 refs., 17 figs., 3 tabs.

Abstract: Pacific Northwest Laboratory (PNL) is developing a low-temperature, catalytic process that converts high-moisture biomass feedstocks and other wet organic substances to useful gaseous and liquid fuels. The advantage of this process is that it works without the need for drying or dewatering the feedstock. Conventional thermal gasification processes, which require temperatures above 750/degree/C and air or oxygen for combustion to supply reaction heat, generally cannot utilize feedstocks with moisture contents above 50 wt %, as the conversion efficiency is greatly reduced as a result of the drying step. For this reason, anaerobic digestion or other bioconversion processes traditionally have been used for gasification of high-moisture feedstocks. However, these processes suffer from slow reaction rates and incomplete carbon conversion. 50 refs., 21 figs., 22 tabs.

Abstract: The biodegradation of lignin, which acts as the main barrier for digestibility of straws in ruminants, has been studied by many investigators using various forms of lignin and different groups of fungi. In the present study, wheat straw-lignin (acid-insoluble) has been used to characterize various mold species for their lignolytic activity with a view to select promising ones for bioconversion of lignocellulosic straws.

Abstract: As stated in the introduction of this thesis, hydroxylated aromatic compounds in general are of great importance for various industries as for instance pharmaceutical, agrochemical and petrochemical industries. Since these compounds can not be isolated in sufficient amounts from natural resources, they have to be synthesized. Chemical synthesis of hydroxylated aromatics is often a difficult task. Direct hydroxylation methods can only be achieved under extreme conditions, while indirect methods often are laborious multi-step processes. Biotechnological formation methods for hydroxylated aromatic compounds are a promissing alternative to the cumbersome organic chemical endeavours. The bioformation of hydroxylated aromatics in principle can be accomplished in four different ways: along biosynthetic routes, by means of direct hydroxylation methods, by replacement of substituents by hydroxyl groups, and by addition and/or modification reactions of side-chains. This research was done to investigate the potential of bacteria or enzymes thereof to form hydroxylated aromatics. To obtain a microorganism which hydroxylates D-phenyIglycine regio- and stereospecifically yielding D-4-hydroxyphenyIglycine, various bacteria were isolated on D-phenyIglycine as sole carbon and energy source. Unfortunately, however, none of the isolates was able to hydroxylate phenylglycine (chapters 1 and 2). Experiments with whole cells and cell extracts showed that the side chain was modified before hydroxylation of the aromatic ring occurred. One of the isolates, Pseudomonas putida LW-4, was also able to grow on D-4-hydroxyphenyIglycine and it was shown that this compound was initially degraded by means of an enantioselective transaminase. Preliminary experiments with partially purified extracts have demonstrated that this reversible enzyme can be used to form D-4-hydroxyphenylglycine from 4-hydroxyphenylglyoxylate (chapter 4). To investigate D-4-hydroxyphenylglycine degradation in general, also other bacteria were isolated on D-4-hydroxyphenylglycine as sole carbon and energy source. One of these isolates, Pseudomonas putida MW27, possessed a D-selective as well as a L-selective 4-hydroxyphenylglycine transaminase (chapter 5). Evidently some microorganisms transaminate both enantiomers of 4-hydroxyphenylglycine and thus are less suitable for the formation of D-4-hydroxyphenylglycine by means of a trans amination. To apply bacteria or enzymes thereof for the hydroxylation of phenylacetate and/or certain hydroxyphenylacetates a thorough knowledge concerning the bacterial metabolism of these compounds is needed. In chapter 6 the degradation of 4-hydroxyphenylacetate by a Xanthobacter species is described and it is shown that this strain can convert 4-hydroxyphenylacetate to 2,5-dihydroxyphenylacetate (homogentisate). To accomplish a formation of homogentisate by whole cells, further degradation of homogentisate had to be blocked by metalchelators. In chapter 7 the degradation of DL-phenylhydracrylic acid and metabolites thereof, by a Flavobacterium species is described. In the presence of dipyridyl these cells converted both 3- and 4-hydroxyphenylacetate to homogentisate. As stated in chapter 7, the internal regeneration of reduction equivalents by using starting compounds which are more reduced than the compound to be hydroxylated, might be an interesting alternative to the simple addition of cosubstrates. The bioformation of cis- ,2-dihydroxycyclohexa-3,5-diene (cis-benzeneglycol) from benzene illustrates the potential of biotransformations. The chemical synthesis of cis-benzeneglycol consists of several steps with a very low yield, whereas the biological formation is a one step process with a high yield. Continuous bioformation of cis-benzeneglycol from benzene by mutant cells growing on succinate under nitrogen-limited conditions in a chemostat, was easily achieved (chapter 8). In order to predict the cis-benzeneglycol concentration at various times, a mathematical model was developed that fitted rather well for both benzene-transport-limited and kinetically limited production conditions. This continuous process, however, resulted in two products: cis-benzeneglycol and cells. In order to make the continuous process economically more attractive, it is necessary to reuse the produced cells. Another problem encountered during the bioproduction of cis-benzeneglycol was the toxicity of benzene; a low benzene concentration was a prerequisite for good performance of the bioconversion process. Incubation experiments with the cis-benzeneglycol-producing mutant showed that hexadecane is a suitable solvent to circumvent benzene toxicity (chapter 9). Moreover, the addition of hexadecane did not significantly effect the rate of cis-benzeneglycol formation. Chapters 10, 11 and 12 deal with the bioformation of 4-hydroxybenzoate from various 4-halobenzoates. Bioformation of 4-hydroxybenzoate was only achieved when whole cells were incubated with the specified 4-halobenzoates under conditions of low and controlled oxygen concentrations. Surprisingly no formation of 4- hydroxybenzoate occurred under anaerobic conditions, this in spite of the fact that such dehalogenases have been demonstrated to be hydrolytic. 4-Hydroxybenzoate was also formed from 2,4-dichlorobenzoate. This latter compound was initially reductively dechlorinated to 4-chlorobenzoate which in turn was converted to 4-hydroxybenzoate (chapter 11). In order to study the feasibility of continuous bioproduction of hydroxyaromatics from haloaromatics, the bioconversion of 4-chlorobenzoate to 4-hydroxybenzoate by cells immobilized in carrageenan was used as a model system. At air saturation the rate of dechlorination was rapidly limited by internal oxygen transport. However, high oxygen concentration resulted in maximal 4-chlorobenzoate dehalogenation, while 4-hydroxybenzoate formation under these conditions was negligible. Consequently, the oxygen concentration has to be strictly controlled to obtain a good production of 4-hydroxybenzoate at an acceptable rate.

Abstract: Application: digestion anaerobie de dechets solides urbains. Recherche des conditions optimales de production d'acides gras volatils en presence d'un inhibiteur de la methanogenese. Communication dans un congres