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PubMed2002

Isolation and characterization of a Trichodermastrain capable of fermenting cellulose to ethanol.

The direct fermentation of cellulosic biomass to ethanol has long been a desired goal. To this end, we screened the environment for fungal strains capable of this conversion when grown on minimal medium. One strain, identified as a member of the genus Trichoderma and designated strain A10, was isolated from cow dung and initially produced about 0.4 g ethanol l(-1). This strain cannot grow on any substrate under anaerobic conditions, but can ferment microcrystalline cellulose or several sugars to ethanol. Ethanol accumulation was eventually increased, by selection and the use of a vented fermentation flask, to 2 g l(-1) when the fermentation was carried out in submerged culture in minimal medium. The highest levels of ethanol, >5.0 g l(-1), were obtained by the fermentation of glucose. Little ethanol was produced by the fermentation of xylose, although other fermentation products such as succinate and acetate were observed. Strain A10 was also found to utilize (aerobically) a wide range of carbon sources. In addition, auxotrophic mutants were generated and used to demonstrate parasexuality by complementation between auxotrophs and between morphological mutants. The ability of this strain to use a wide variety of carbohydrates (including crystalline cellulose) combined with its minimal nutrient requirements and the availability of a genetic system suggests that the strain merits further investigation of its ability to convert biomass to ethanol.

Cellulose↗
PubMed1993

A nonferrous instrumental joystick device for recording behavioral responses during magnetic resonance imaging and spectroscopy.

A nonferrous joystick device was developed to permit subjects to continuously report ethanol-induced alterations in subjective mood states while undergoing a magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) procedure. The device utilizes air pressure (supplied by a small compressor) that is directed to a series of tubes that terminate in a hand-held unit. The hand-held unit easily fits inside the magnet and resembles a standard computer game joystick except that the ends of the air hoses replace the buttons. The control unit contains three pressure transducers, which are triggered when the tubes are occluded by the subject, activating different pens on an event marker located 6 m from the whole body imager. The unit is safe to use inside a 1.5-Tesla magnetic field and does not disrupt the MRI and MRS recording procedures. Subjective reports of ethanol-induced euphoria and intoxication paralleled the MRS detection of ethanol in the brain. This device could prove to be useful in numerous behavioral studies involving whole-body MRI and MRS.

Adult↗
PubMed1975

Studies on the energy metabolism during the respiratory process by baker's yeast.

Microcalorimetry, in combination with conventional methods for determining metabolic activity, opens the possibility to study the efficiency with which ATP, produced as a result of metabolic activity, is utilized by the cell for energy-requiring synthetic reactions. Using commercial baker's yeast as a test organism and glucose, ethanol, acetic and lactic acids as substrates, the fate of the ATP produced by the respiratory process was studied by measuring oxygen consumption (using the Warburg technique) and the corresponding heat development (using the LKB Flow-Microcalorimeter). From these data heat development per mm3 oxygen consumed was calculated. Values obtained should fall within a heat production range that can be calculated from the combustion heat of the process (maximum heat development) and maximum energy conservation, assuming full participation of ATP in energy-requiring synthetic reactions (minimum heat development). It was found that during the respiratory process of "resting" cells of baker's yeast, regardless of the substrate used, heat development was close to the maximum value inherent with substrate oxidation. Consequently, practically all ATP, produced as a result of the respiratory process, is de-phosphorylated under heat development and thus is not (or very inefficiently) utilized for energy-requiring synthetic reactions. In accordance with this conclusion it was found that addition of 2-4-DNP, a powerful uncoupler of phosphorylation from the respiratory process, did not result in an appriciable increase in heat development. Even in the presence of an assimilable N source, allowing unrestricted growth, initially only a very small percentage of the ATP produced is utilized for synthetic processes. A gradual improvement of this poor economic ATP utilization was observed during the prelogarithmic growth phase. As a possible explanation of this wasteful aerobic metabolism of baker's yeast and its restricted ability to utilize ATP for synthetic processes was mentioned the exceptional low content of messenger RNA, typical for a baker's yeast subjected to a ripening process before harvesting.

Dinitrophenols↗
PubMed2006

Ethanol-induced apoptosis in polarized hepatic cells possibly through regulation of the Fas pathway.

BACKGROUND: It has been noted that alcohol-related liver diseases can be associated with an increase in apoptotic hepatocellular death. Moreover, the promotion of hepatocyte apoptosis may be linked to signals emanating from death receptors, particularly Fas [CD95/apoptosis-inducing protein 1 (APO-1)]. In the present study, we utilized an in vitro hepatic culture model [hybrid of human fibroblast (WI 38) and rat hepatoma (Fao) cells, WIF-B cells] to study potential contributing mechanisms involved in hepatocellular apoptosis following ethanol administration. METHODS: WIF-B cultures (differentiated hepatic cells that efficiently metabolize alcohol) were treated with or without ethanol and specific inhibitors of alcohol metabolism and cysteine protease activity, followed by morphological and biochemical examination of proapoptotic parameters. RESULTS: The results of this work demonstrated that ethanol administration leads to an increase (45%-60%) in caspase-3 activity and that the induction of apoptosis was found to be linked to the metabolism of alcohol. Additionally, increases were observed in the activity of upstream initiator caspases (caspase-2 and caspase-8) that are directly related to membrane signaling events of death receptors such as Fas. Moreover, it was determined that the activation of caspase-3 could be blocked by the presence of a specific caspase-8 inhibitor, again linking death receptor-associated proteases to downstream effector caspase activity in alcohol-related death. Finally, ethanol administration was found to result in an increase in the amount of Fas protein present in the membrane fraction of the cell. The increase in membrane Fas protein indicates ligand-independent membrane targeting of Fas in the alcohol-treated cells that could potentially be a key signaling event in the induction of the proapoptotic caspase cascade. CONCLUSIONS: The data presented here indicate that alcohol metabolism induces apoptosis in WIF-B cells that occurs, in part, by mechanisms involving signals emanating from death receptors.

Antimetabolites↗
PubMed2007

Glucose-induced production of recombinant proteins in Hansenula polymorpha mutants deficient in catabolite repression.

The most commonly used expression platform for production of recombinant proteins in the methylotrophic yeast Hansenula polymorpha relies on the strong and strictly regulated promoter from the gene encoding peroxisomal enzyme alcohol (or methanol) oxidase (P(MOX)). Expression from P(MOX) is induced by methanol and is partially derepressed in glycerol or xylose medium, whereas in the presence of hexoses, disaccharides or ethanol, it is repressed. The need for methanol for maximal induction of gene expression in large-scale fermentation is a significant drawback, as this compound is toxic, flammable, supports a slow growth rate and requires extensive aeration. We isolated H. polymorpha mutants deficient in glucose repression of P(MOX) due to an impaired HpGCR1 gene, and other yet unidentified secondary mutations. The mutants exhibited pronounced defects in P(MOX) regulation only by hexoses and xylose, but not by disaccharides or ethanol. With one of these mutant strains as hosts, we developed a modified two-carbon source mode expression platform that utilizes convenient sugar substrates for growth (sucrose) and induction of recombinant protein expression (glucose or xylose). We demonstrate efficient regulatable by sugar carbon sources expression of three recombinant proteins: a secreted glucose oxidase from the fungus Aspergillus niger, a secreted mini pro-insulin, and an intracellular hepatitis B virus surface antigen in these mutant hosts. The modified expression platform preserves the favorable regulatable nature of P(MOX) without methanol, making a convenient alternative to the traditional system.

Alcohol Oxidoreductases↗
PubMed2006

Adaptation of a recombinant xylose-utilizing Saccharomyces cerevisiae strain to a sugarcane bagasse hydrolysate with high content of fermentation inhibitors.

Adaptation of a xylose-utilizing genetically engineered strain of Saccharomyces cerevisiae to sugarcane bagasse hydrolysates by cultivation during 353h using medium with increasing concentrations of inhibitors, including phenolic compounds, furaldehydes and aliphatic acids, led to improved performance with respect to ethanol production. The remaining xylose concentration in the medium at the end of the cultivation was 5.2g l(-1), while it was 11gl(-1) in the feed, indicating that approximately half of the xylose was consumed. The performance of the adapted strain was compared with the parental strain with respect to its ability to ferment three bagasse hydrolysates with different inhibitor concentration. The ethanol yield after 24h of fermentation of the bagasse hydrolysate with lowest inhibitor concentration increased from 0.18gg(-1) of total sugar with the non-adapted strain to 0.38gg(-1) with the adapted strain. The specific ethanol productivity increased from 1.15g ethanol per g initial biomass per h with the non-adapted strain to 2.55gg(-1) h(-1) with the adapted strain. The adapted strain performed better than the non-adapted also in the two bagasse hydrolysates containing higher concentrations of inhibitors. The adapted strain converted the inhibitory furaldehydes 2-furaldehyde (furfural) and 5-hydroxymethyl-2-furaldehyde (HMF) at a faster rate than the non-adapted strain. The xylose-utilizing ability of the yeast strain did not seem to be affected by the adaptation and the results suggest that ethanol rather than xylitol was formed from the consumed xylose.

Adaptation, Physiological↗
PubMed1995

Effect of chronic ethanol consumption on the energy state and structural stability of periportal and perivenous hepatocytes.

This study was implemented to evaluate whether perivenous cells experience functional alterations due to a deficit in oxygen tension resulting from ethanol oxidation in the periportal regions of the lobule. Periportal and perivenous hepatocytes were prepared from ethanol-fed and control animals (Lieber-DeCarli diet, 31 days). These cells were either incubated at various oxygen tensions by varying the composition of the gases utilized to equilibrate the incubation buffers (0, 5, 25, and 95% oxygen) or they were unincubated. They were analyzed for adenine nucleotide and inorganic phosphate concentrations and from these data phosphorylation potentials and energy charge values were determined. Under highly aerobic conditions no differences were observed in the energy states of the cells irrespective of their source (control vs ethanol-fed; periportal vs perivenous). The ATP concentrations, phosphorylation potentials, and energy charge values indicated that the energy states of cells from both ethanol-fed and control rats were maintained at relatively high levels in incubations with 5 and 25% oxygen. However, unincubated cells and those incubated at 0% oxygen demonstrated lowered energy states and the decreases were most striking in hepatocytes from ethanol-fed animals. Measurements of LDH loss and trypan blue exclusion indicate that cell leakage and viability loss occur when cells are incubated under anoxic and hypoxic conditions. At low oxygen tensions perivenous cells from ethanol-fed rats demonstrated much greater loss of structural stability than did the other cell preparations. These observations indicate that decreased energy state is one factor which contributes to cell damage in hepatocytes from ethanol-fed animals. Moreover, perivenous cells from ethanol-fed animals seem to be particularly vulnerable to damage under hypoxic conditions.

Adenosine Diphosphate↗
PubMed1984

Ethanol-ascorbate interrelationship in acute and chronic alcoholism in the guinea pig.

The effects of low (200 ppm) and of high (2000 ppm) ascorbic acid, in a nutritionally adequate diet, on blood ethanol levels have been studied in permanently carotid-cannulated, ethanol-infused, unanesthetized guinea pigs. In the acute study, the postinfusion rate of ethanol decline in the blood of animals treated with ascorbic acid was significantly higher when compared with animals treated with fructose, and the rate in the two treated groups was significantly higher than in untreated controls. In the chronic study, animals were infused with sublethal doses of ethanol (30% of the total caloric intake) for 8 weeks. Blood ethanol levels monitored throughout this period showed, at 3 hr postinfusion, a lower concentration in the group on a high ascorbic acid diet. Both experimental groups receiving ethanol lost significantly more body weight in the second week of dieting; but, while the group on high ascorbic acid regained weight steadily thereafter, the group on low ascorbic acid was still 50 g below the controls at the end of the experiment. Liver, kidney, and adrenal ascorbic acid concentrations were lower in the ethanol-treated groups compared to controls. Examination of the liver revealed more fatty metamorphosis or steatosis in the low ascorbic acid group, but there was no evidence of liver fibrosis or cirrhosis. These results demonstrate the feasibility of utilizing the guinea pig for the study of the biochemical and morphological sequelae of alcoholism. They further support the contention that a diet which is nutritionally adequate may no longer be so in the presence of high ethanol intake, and that supplemental vitamin C ingestion may afford protection against ethanol toxicity.

Adrenal Glands↗
PubMed1982

Benzo(a)pyrene phenol production by perfused rat liver and its inhibition by ethanol.

A rapid and inexpensive method has been developed to estimate rates of benzo(a)pyrene phenol production by perfused rat liver. This method is based on the measurement of benzo(a)pyrene phenols utilizing a simple fluorometric procedure. Within 2 to 3 min after infusion of benzo(a)pyrene bound to serum albumin, phenols are excreted into the perfusate, primarily as glucuronide and sulfate conjugates. Maximal rates of phenol release were 8 to 10 nmol/g/hr in livers from control rats and 40 to 42 nmol/g/hr in livers from 3-methylcholanthrene-treated rats. Fasting of 3-methylcholanthrene-treated rats for 24 hr prior to perfusion experiments did not affect either the rate of phenol production or the extent of their conjugation. Ethanol (20 mM) inhibited rates of phenol formation by 50% in livers from fasted, 3-methylcholanthrene-treated rats but had no effect on benzo(a)pyrene hydroxylase activity in isolated hepatic microsomes. These data indicate that ethanol inhibits phenol formation from benzo(a)pyrene in intact liver, probably by diminishing the supply of the cofactor reduced nicotinamide adenine dinucleotide phosphate.

Animals↗
PubMed1996

N-nitrosodimethylamine-derived O(6)-methylguanine in DNA of monkey gastrointestinal and urogenital organs and enhancement by ethanol.

N-nitrosodimethylamine (NDMA) is a human cancer initiator suspect. Ethanol, a cancer risk factor, may synergize with nitrosamines by suppressing hepatic clearance, to increase internal exposure. A limitation to these hypotheses is lack of activation of NDMA by many rodent tissues. However, systemtic primate studies are lacking. Patas monkeys were utilized to investigate NDMA activation by primate tissues in vivo, generating the promutagenic DNA lesion 0(6)-methylguanine (0(6)-meG). Adult monkeys received 0. 1 mg/kg NDMA by gavage, in some cases preceded by ethanol. Four hours after NDMA only, 0(6)-meG was detected in DNA from all tissues. Levels were highest in gastric mucosa and liver and were only about 50% lower in DNA from white blood cells, esophagus, ovary, pancreas, urinary bladder and uterus. With ethanol co-exposure, amounts of 0(6)-meG increased at least 2-fold in all tissues except liver. The largest effect was in esophagus (17-fold increase), followed by ovary, large intestine, urinary bladder, spleen and cerebellum (9- to 13-fold increases), and uterus, cerebrum and brain stem (7- to 8-fold increases). Alkylguanine alkyltransferase activities varied over a 30-fold range and were highest in liver and stomach. Thus primate tissues, especially those of the gastrointestinal and urogenital organs, are sensitive targets for DNA adduct damage due to NDMA, and ethanol co-exposure leads to striking increases in adducts. Our data support epidemiology implicating nitrosamines in causation of cancers of stomach and other organs, and alcohol as enhancing internal exposure to nitrosamines.

Alkylation↗
PubMed2004

Anaerobic bio-hydrogen production from ethanol fermentation: the role of pH.

Hydrogen was produced by an ethanol-acetate fermentation at pH of 5.0 +/- 0.2 and HRT of 3 days. The yield of hydrogen was 100-200 ml g Glu(-1) with a hydrogen content of 25-40%. This fluctuation in the hydrogen yield was attributed to the formation of propionate and the activity of hydrogen utilizing methanogens. The change in the operational pH for the inhibition of this methanogenic activity induced a change in the main fermentation pathway. In this study, the main products were butyrate, ethanol and propionate, in the pH ranges 4.0-4.5, 4.5-5.0 and 5.0-6.0, respectively. However, the activity of all the microorganisms was inhibited below pH 4.0. Therefore, pH 4.0 was regarded as the operational limit for the anaerobic bio-hydrogen production process. These results indicate that the pH plays an important role in determining the type of anaerobic fermentation pathway in anaerobic bio-hydrogen processes.

Acetates↗
PubMed1991

The crystal and molecular structure of VH amylose by electron diffraction analysis.

The crystal and molecular structures of VH amylose were determined by a constrained linked-atom least-squares refinement, utilizing intensities measured from electron diffraction patterns and stereochemical restraints. Hexagonal platelet single crystals were grown from dilute aqueous ethanol solution and their electron diffraction diagrams analysed. These data indicated that the amylose chains were crystallized in a hexagonal lattice with a = b = 13.65 A, c (chain axis) = 8.05 A and space group P6(5)22. The best model obtained using the base plane data coupled with a stereochemical refinement yielded R = 0.24 (R'' = 0.25). It corresponded to a system of left-handed 6-fold helices packed on an hexagonal net but with statistically random up/down chain disorder. A column of six water molecules was present within each helical repeat. Additionally, the gap between each pair of adjacent helices was bridged by two water molecules positioned so as to allow hydrogen bonding with chains of either sense. This proposed crystal structure differs somewhat from previous reports which invoked orthorhombic lattices and requires a regularly alternating arrangement of up and down chains to account for the intensity. Suggestions are made to account for these differences.

Amylose↗
PubMed2006

The removal of Cremophor EL from paclitaxel for quantitative analysis by HPLC-UV.

A novel method for analysis of hydrophobic drug molecules in matrices that contain Cremophor EL (CrEL) is presented. The method utilized a precipitation technique involving mercuric chloride in a reaction with CrEL to form an insoluble complex in an ethanol matrix. The hydrophobic drug molecule was then analyzed by HPLC-UV without interference from CrEL. Nuclear magnetic resonance and infrared spectroscopy indicated that the mechanism of precipitation involves the reaction of mercuric chloride with the ether bond of CrEL. Analysis by HPLC with UV detection of paclitaxel and related substances was used to verify that the reaction is specific toward CrEL.

Chemistry, Pharmaceutical↗
PubMed2005

Electrochemical method for the detection of lipase activity.

A novel electrochemical technique for the general assay of lipase activity is described. The method utilizes a solid-supported lipase substrate, which is formed by dripping and drying a small amount of an ethanol solution of 9-(5'-ferrocenylpentanoyloxy)nonyl disulfide (FPONDS) onto gold modified by a hexanethiol self-assembled monolayer. The redox ferrocene group of FPONDS generates the electrochemical signal, the intensity of which is proportional to the number of FPONDS molecules at the interface. Electrochemical and surface-enhanced infrared absorption spectroscopic data, as well as control experiments with an engineered, deactivated mutant enzyme, demonstrate that the wild-type lipase from Thermomyces lanuginosus is capable of cleaving the ester bonds of FPONDS molecules via an enzymatic hydrolysis mechanism, which includes the adsorption of the lipase onto the substrate surface. The hydrolysis liberates the ferrocene groups from the interface triggering a decay of the electrochemical redox signal. The rate of the electrochemical signal decrease is proportional to the lipase activity/concentration. These data suggest a general method for the direct measure of enzymatic activity of lipases.

Disulfides↗
PubMed2003

Inhibition of alcohol-associated colonic hyperregeneration by alpha-tocopherol in the rat.

BACKGROUND: Chronic alcohol consumption results in colorectal mucosal hyperregeneration, a condition associated with an increased risk for colorectal cancer. Possible mechanisms may involve the effects of acetaldehyde and/or free radicals generated during alcohol metabolism. Vitamin E is part of the antioxidative defense system, and its concentration is decreased or its metabolic utilization increased in various tissues after chronic alcohol consumption. We wondered whether alpha-tocopherol supplementation may prevent ethanol-induced colorectal cell cycle behavior and whether these changes were related to alterations in protein synthesis. METHODS: Five groups of male Wistar rats, each consisting of 14 animals, received liquid diets as follows: group 1, alcohol; group 2, alcohol + alpha-tocopherol; group 3, control (i.e., isocaloric glucose); group 4; control (i.e., isocaloric glucose) + alpha-tocopherol. Group 5 was fed a solid chow diet ad libitum. After 4 weeks of feeding, immunohistology was performed with anti-proliferating cell nuclear antigen (PCNA) or anti-BCL2 antibodies. Fractional (k(s)) and absolute (V(s)) rates of protein synthesis and rates of protein synthesis relative to RNA (k(RNA)) and DNA (k(DNA)) were measured with a flooding dose of L-[4-3H] phenylalanine with complementary analysis of protein and nucleic acid composition. RESULTS: The PCNA index was increased significantly in the colon after ethanol administration compared with controls (ethanol, 10.3 +/- 2.3 vs. control, 6.51 +/- 1.6% PCNA positive cells, p < 0.05), although neither the protein, RNA, and DNA concentrations nor k(s), k(RNA), k(DNA), and V(s) were affected. This increase in PCNA index was significantly diminished by coadministration of alpha-tocopherol (ethanol + alpha tocopherol, 7.86 +/- 1.71% PCNA positive cells, p < 0.05) without significant alterations in protein synthetic parameters. A similar result was obtained for the PCNA index in the rectal mucosa (ethanol, 14.6 +/- 4.4 vs. control, 12.1 +/- 4.2% PCNA positive cell), although this did not reach statistical significance. Neither ethanol nor alpha tocopherol feeding had any significant effect on BCL-2 expression in the colorectal mucosa. As with the colon, protein synthetic parameters in the mucosa were not affected by alcohol feeding at 4 weeks. These effects on colonic cell turnover without corresponding changes in protein synthesis thus represent a specific localized phenomenon rather than a general increase in anabolic processes in the tissue and reaffirm the hyperregenerative properties of chronic alcohol consumption. CONCLUSIONS: Alcohol-associated hyperproliferation could be prevented, at least in part, by supplementation with alpha-tocopherol. This may support the hypothesis that free radicals are involved in the pathogenesis of alcohol-associated colorectal hyperproliferation.

Animals↗
PubMed1996

Characterization of a new obligately anaerobic thermophile, Thermoanaerobacter wiegelii sp. nov.

An obligately anaerobic, extremely thermophilic Thermoanaerobacter species was isolated from a freshwater pool formed from a geothermally heated (56 to 69 degrees C) water outlet in Government Gardens, Rotorua, New Zealand. This organism was a spore-forming, gram-negative, rod-shaped bacterium. Strain Rt8.B1T (= DSM 10319T) (T = type strain) fermented a wide variety of mono-, di-, and polysaccharides and produced ethanol, acetate, lactate, propionate, and hydrogen. Sugar alcohols were also fermented, but organic acids and amino acids were not utilized. On the basis of its morphological characteristics, DNA G + C content, obligately anaerobic, thermophilic, polysaccharolytic nature, and levels of 16S rRNA sequence homology, we propose that strain Rt8.B1T should be classified in the genus Thermoanaerobacter as a new species, Thermoanaerobacter wiegelii.

Bacteria, Anaerobic↗
PubMed1984

The characterization of somatomedin A, isolated by microcomputer-controlled chromatography, reveals an apparent identity to insulin-like growth factor 1.

The polypeptide termed somatomedin A (SMA) was isolated from outdated human plasma by a new purification procedure, not using acid ethanol extraction. Fractions containing SMA were monitored by a placenta radioreceptorassay and a radioimmunoassay for SMA. The purification method utilized a microcomputer-controlled chromatography system, yielding both SMA (identified as insulin-like growth factor 1 (IGF-1) or a deamidated derivative) and insulin-like growth factor 2 (IGF-2). The first step of CM-Affigel blue adsorbed at neutral pH the majority of somatomedins detectable by the radioreceptorassay for SMA. Exclusion chromatography on Sephadex G-50 in 0.1 M acetic acid separated this active material from albumin and NaCl. Separation between SMA and IGF-2 was achieved on two different cation-exchange columns, but not in the final high-performance liquid chromatography step. The isoelectric points, determined by chromatofocusing, were 8.0 for SMA and 6.2 for IGF-2. The amino acid compositions of the two isolated peptides were indistinguishable from the known compositions of IGF-1 and IGF-2. Sequence analysis up to position 39 of the peptide with a pI of 6.2 also proved identity with IGF-2 for all positions examined. The peptide with a pI of 8.0, corresponding to SMA, was degraded directly as well as after CNBr cleavage. The results show that it is identical to IGF-1, with the possible exception of acid/amide assignment, which could correspond to a deamidation. If occurring in the native preparation before analysis, it could explain the chromatographic properties and isoelectric point of SMA versus IGF-1 isolated by other techniques.

Amino Acid Sequence↗
PubMed1985

Differences in Xylan Degradation by Various Noncellulolytic Thermophilic Anaerobes and Clostridium thermocellum.

Hemicellulose fractions with a predetermined distribution of xylose, xylooligomers, and xylan fractions were obtained through steam explosion of wood by the steam explosion-extraction process of BFA-Hamburg, Hamburg, Federal Republic of Germany. A differential utilization of various molecular-weight fractions by several thermophilic anaerobic bacteria was determined during their growth on the hemicellulose preparations. Clostridium thermocellum (60 degrees C) first utilized the high-molecular-weight fractions (polymerization degree of 15 to 40 xylose units). Xylose and xylooligomers of n = 2 to 5 accumulated while C. thermocellum was not growing, as evident from the fermentation products formed. Whereas the xylan was hydrolyzed and the small oligoxylans were utilized after more than 100 h of incubation, xylose was not significantly utilized. In contrast to this, C. thermohydrosulfuricum (70 degrees C) and Thermoanaerobium brockii (70 degrees C) utilized xylose first and then xylooligomers of n = 2 to 5, but xylooligomers of n greater than 6 were only slowly utilized. Thermoanaerobacter ethanolicus (70 degrees C), Thermobacteroides acetoethylicus (70 degrees C), and C. thermosaccharolyticum (60 degrees C) utilized xylose preferentially. Xylooligomers of n = 2 to 5 and n = 6 and greater were apparently concomitantly utilized without significant differences. In contrast to C. thermocellum, the non-cellulolytic organisms grew during xylan hydrolysis, producing ethanol, lactate, acetate, CO(2), and H(2).

Journal Article↗