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ABSTRACT: The processes of separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) were employed using Saccharomyces cerevisiae for the production of ethanol from cassava pulp without any pretreatment. A combination of amylase, cellulase, cellobiase, and glucoamylase produced the highest levels of ethanol production in both the SHF and the SSF method. A temperature of 37 °C, a pH of 5.0, and an inoculum size of 6% were the optimum conditions for SSF. For the batch process at a pulp concentration of 20%, ethanol production levels from SHF and SSF were the highest, at 23.51 and 34.67 g L(-1) respectively, but in the fed-batch process, the levels of ethanol production from SHF and SSF rose to 29.39 and 43.25 g L(-1) respectively, which were 25% and 24.7% higher than those of the batch process. Thus SSF using the fed-batch provided a more efficient method for the utilization of cassava pulp.
Bioscience Biotechnology and Biochemistry 04/2012; 76(4):671-8. · 1.28 Impact Factor
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ABSTRACT: A biphasic fermentation approach was undertaken for the production of ethanol and hydrogen from cassava pulp. The glucose generated by co-culture of Clostridium thermocellum and Thermoanaerobacterium aotearoense was 13.65±0.45 g L(-1), which was 1.75 and 1.17-fold greater than that produced by mono-cultures of C. thermocellum and T. aotearoense, respectively. The accumulated glucose could be utilised rapidly by subsequently inoculated Saccharomyces cerevisiae. An inoculum ratio of 1:1, a thermophilic fermentation of 84 h, and a pulp concentration of 4% proved optimal for ethanol production, fermentation efficiency, and productivity. With these conditions, the ethanol level reached 8.83±0.31 g L(-1) with a fermentation efficiency of 64.95±2.71%. Hydrogen production of 4.06 mmol by the co-culture system was 1.54 and 2.09-fold greater than that produced by mono-cultures of C. thermocellum and T. aotearoense, respectively. This sequential co-culture approach provided a consolidated bio-processing means to produce ethanol and hydrogen from cassava pulp.
Bioresource technology 09/2011; 102(22):10471-9. · 4.25 Impact Factor
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ABSTRACT: Clostridium thermocellum is a model microorganism for converting cellulosic biomass into fuels and chemicals via consolidated bioprocessing. One of the challenges for industrial application of this organism is its low ethanol tolerance, typically 1-2% (w/v) in wild-type strains. In this study, we report the development and characterization of mutant C. thermocellum strains that can grow in the presence of high ethanol concentrations. Starting from a single colony, wild-type C. thermocellum ATCC 27405 was sub-cultured and adapted for growth in up to 50 g/L ethanol using either cellobiose or crystalline cellulose as the growth substrate. Both the adapted strains retained their ability to grow on either substrate and displayed a higher growth rate and biomass yield than the wild-type strain in the absence of ethanol. With added ethanol in the media, the mutant strains displayed an inverse correlation between ethanol concentration and growth rate or biomass yield. Genome sequencing revealed six common mutations in the two ethanol-tolerant strains including an alcohol dehydrogenase gene and genes involved in arginine/pyrimidine biosynthetic pathway. The potential role of these mutations in ethanol tolerance phenotype is discussed.
Applied Microbiology and Biotechnology 08/2011; 92(3):641-52. · 3.42 Impact Factor
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ABSTRACT: To enhance ethanol production in Thermoanaerobacterium aotearoense, the lactate dehydrogenase (ldh) gene, which is responsible for lactic acid production in a key branch pathway, was successfully disrupted via homologous recombination. ldh-up and ldh-down were designed and amplified based on JW/SL-YS485-AY 278026, and they were subsequently used as homologous fragments with an inserted erythromycin resistance gene to construct the targeted vector based on pBLUESCRIPT II SK(+). Southern hybridization and PCR-based assay definitely confirmed that the ldh gene in the Δldh mutant was disrupted by the insertion of the erythromycin resistance gene. Compared with the wild type, the Δldh mutant exhibited increases of 31.0% and 31.4% in cell yield under glucose and xylose cultivation, respectively, probably because knocking out the ldh gene results in increased acetate and ATP levels. Knockout of lactate dehydrogenase produced 2.37- and 2.1-fold increases in the yield of ethanol (mole/mole substrate) under glucose and xylose cultivation, respectively. Moreover, no lactic acid was detected in Δldh mutant fermentation mixtures (detection limit of HPLC: 0.5 mM), but lactic acid was readily detected for growth of the wild-type strain on both glucose and xylose, with final concentrations up to 59.24 mM and 56.06 mM, respectively. The success of this process thoroughly demonstrates the methodological possibility of gene knockout through homologous recombination in Thermoanaerobacterium.
Enzyme and microbial technology. 02/2011; 48(2):155-61.
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ABSTRACT: A strictly anaerobic, thermoacidophilic, H(2)-producing bacterium was isolated and designated as Thermoanaerobacterium aotearoense. The optimized cultivation conditions for H(2) production are 55 degrees C, pH 6.5 and 10gl(-1) of glucose or xylose. A metabolic pathway analysis showed that lactate occupied most of the liquid metabolites and consumed a large amount of NADH. To increase the efficiency of hydrogen production, the gene encoding the l-lactate dehydrogenase was knocked out to redirect the NADH flow. Genetic manipulation resulted in the 2 and 2.5 folds increase of the H(2) yield and production rate, respectively. The maximum H(2) yields using the Deltaldh mutant were 2.71, 1.45 and 2.28molH(2)mol(-1) sugar under glucose, xylose and glucose/xylose mixture tests, respectively. The recombinant Deltaldh strain could ferment the mixture of glucose and xylose to produce H(2) effectively, indicating that the performance of Thermoanaerobacterium in H(2) production can be significantly improved by metabolic engineering technique.
Bioresource technology 11/2010; 101(22):8718-24. · 4.25 Impact Factor
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ABSTRACT: In our laboratory, one Monascus anka mutant able to produce high yield of yellow pigments screened by physical and chemical combination mutagenesis was obtained.
This study evaluated peptone, NH4NO3 and KH2PO4 as the most significant variables for Monascus yellow pigment production by this M. anka mutant MYM in submerged fermentation. Response surface methodology (RSM) optimized these nutrient parameters for maximum
yellow pigment production (87.24OD units), which resulted at 10.3g/L peptone, 11.9g/L NH4NO3 and 4.7g/L KH2PO4 in the medium. According to the fitting equation, through five replication experiments under the optimized conditions, the
average yellow pigment production obtained was 88.14 OD units for flask cultivation and 92.45 OD units for 5L fermenter cultivation.
Meanwhile, the citrinin could not be detected by HPLC method.
European Food Research and Technology 03/2009; 228(6):895-901. · 1.57 Impact Factor
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ABSTRACT: To study the changes of vitamin nutritional status of residents in a high-risk area of esophageal cancer.
8 towns where nutrition survey had been done were selected, 2 villages were randomly selected from each town and 30 families were randomly selected per village. The blood and 4h burden urine samples were collected from subjects. The serum vitamin A, blood total ascorbic acid and glutathione reductase activition coefficient (AC) in red blood cell were determinde by using of trifluoroacetic acid colorimetry, 2, 4-dinitrophenylhydrazine colorimetric method and Sauberlich method respectively. The contents of vitamin B2 , reduction ascorbic acid and total ascorbic acid in 4h burden urine were measured by using of fluorescent pectrophotometry,2,6-Dichloro-N-(4-hydroxyphenyl)-1,4-benzoquinoneimine titrimetric method and 2,4-dinitrophenylhydrazine colorimetric method respectively. The results were analyzed and compared with those of in 1980, 1983 and 1984. The t-test or chi2-test was carried out.
The level of serum retinal in residents living in Ren cun, Dongyao and Hejian is significantly higher than that of in 1982 (P < 0.01). The level of vitamin B2 in 4h burden urine in residents living in Yaocun, Rencun and Heshun are significantly higher than that of in 1982 or 1984 (P < 0.01). The number of ribflavin deficiency of population living in Dongyao, Hejian, Yaocun and Rencun are significantly lower than that of in 1982 or 1983 (P < 0.01) according to the content of 4h burden urine and glutathione reductase activation coefficient (AC) in red blood cell; the number of vitamin C deficiency of population living in Dongyao, Hejian,Yao cun, Ren cun and Heshun are significantly lower than that of in 1982 or 1983 (P < 0.01) according to blood total ascorbic acid and the ascorbic acid content of 4h-burden urine and.
Vitamin nutritional status of residents in a high-risk area of esophageal cancer have been improved.
Wei sheng yan jiu = Journal of hygiene research 12/2007; 36(6):719-21.
