ABSTRACT
Abstract High potential, thermotolerant, ethanol-producing yeasts were successfully isolated in this study. Based on molecular identification and phylogenetic analysis, the isolated thermotolerant yeasts were clustered in the genera of Pichia kudriavzevii, Candida tropicalis, Candida orthopsilosis, Candida glabrata and Kodamea ohmeri. A comparative study of ethanol production using 160 g/L glucose as a substrate revealed several yeast strains that could produce high ethanol concentrations at high temperatures. When sugarcane bagasse (SCB) hydrolysate containing 85 g/L glucose was used as a substrate, the yeast strain designated P. kudriavzevii RZ8-1 exhibited the highest ethanol concentrations of 35.51 g/L and 33.84 g/L at 37 °C and 40 °C, respectively. It also exhibited multi-stress tolerance, such as heat, ethanol and acetic acid tolerance. During ethanol fermentation at high temperature (42 °C), genes encoding heat shock proteins (ssq1 and hsp90), alcohol dehydrogenases (adh1, adh2, adh3 and adh4) and glyceraldehyde-3-phosphate dehydrogenase (tdh2) were up-regulated, suggesting that these genes might play a crucial role in the thermotolerance ability of P. kudriavzevii RZ8-1 under heat stress. These findings suggest that the growth and ethanol fermentation activities of this organism under heat stress were restricted to the expression of genes involved not only in heat shock response but also in the ethanol production pathway.
Subject(s)
Ethanol/metabolism , Hot Temperature , Pichia/metabolism , Biotransformation , Candida/classification , Candida/isolation & purification , Candida/metabolism , Pichia/classification , Pichia/isolation & purification , Plant Extracts/metabolism , Saccharum/metabolism , Stress, PhysiologicalABSTRACT
Abstract Ethanol production from sweet sorghum juice (SSJ) using the thermotolerant Saccharomyces cerevisiae strain DBKKUY-53 immobilized in an alginate-loofah matrix (ALM) was successfully developed. As found in this study, an ALM with dimensions of 20 × 20 × 5 mm3 is effective for cell immobilization due to its compact structure and long-term stability. The ALM-immobilized cell system exhibited greater ethanol production efficiency than the freely suspended cell system. By using a central composite design (CCD), the optimum conditions for ethanol production from SSJ by ALM-immobilized cells were determined. The maximum ethanol concentration and volumetric ethanol productivity obtained using ALM-immobilized cells under the optimal conditions were 97.54 g/L and 1.36 g/L h, respectively. The use of the ALM-immobilized cells was successful for at least six consecutive batches (360 h) without any loss of ethanol production efficiency, suggesting their potential application in industrial ethanol production.
Subject(s)
Saccharomyces cerevisiae/metabolism , Industrial Microbiology/methods , Sorghum/microbiology , Ethanol/metabolism , Saccharomyces cerevisiae/chemistry , Cells, Immobilized/metabolism , Cells, Immobilized/chemistry , Sorghum/metabolism , Sorghum/chemistry , Ethanol/analysis , Alginates/chemistry , FermentationABSTRACT
Abstract Ethanol production from sweet sorghum juice (SSJ) using the thermotolerant Saccharomyces cerevisiae strain DBKKUY-53 immobilized in an alginate-loofah matrix (ALM) was successfully developed. As found in this study, an ALM with dimensions of 20 × 20 × 5 mm3 is effective for cell immobilization due to its compact structure and long-term stability. The ALM-immobilized cell system exhibited greater ethanol production efficiency than the freely suspended cell system. By using a central composite design (CCD), the optimum conditions for ethanol production from SSJ by ALM-immobilized cells were determined. The maximum ethanol concentration and volumetric ethanol productivity obtained using ALM-immobilized cells under the optimal conditions were 97.54 g/L and 1.36 g/L h, respectively. The use of the ALM-immobilized cells was successful for at least six consecutive batches (360 h) without any loss of ethanol production efficiency, suggesting their potential application in industrial ethanol production.
ABSTRACT
Abstract The application of high-potential thermotolerant yeasts is a key factor for successful ethanol production at high temperatures. Two hundred and thirty-four yeast isolates from Greater Mekong Subregion (GMS) countries, i.e., Thailand, The Lao People's Democratic Republic (Lao PDR) and Vietnam were obtained. Five thermotolerant yeasts, designated Saccharomyces cerevisiae KKU-VN8, KKU-VN20, and KKU-VN27, Pichia kudriavzevii KKU-TH33 and P. kudriavzevii KKU-TH43, demonstrated high temperature and ethanol tolerance levels up to 45 °C and 13% (v/v), respectively. All five strains produced higher ethanol concentrations and exhibited greater productivities and yields than the industrial strain S. cerevisiae TISTR5606 during high-temperature fermentation at 40 °C and 43 °C. S. cerevisiae KKU-VN8 demonstrated the best performance for ethanol production from glucose at 37 °C with an ethanol concentration of 72.69 g/L, a productivity of 1.59 g/L/h and a theoretical ethanol yield of 86.27%. The optimal conditions for ethanol production of S. cerevisiae KKU-VN8 from sweet sorghum juice (SSJ) at 40 °C were achieved using the Box-Behnken experimental design (BBD). The maximal ethanol concentration obtained during fermentation was 89.32 g/L, with a productivity of 2.48 g/L/h and a theoretical ethanol yield of 96.32%. Thus, the newly isolated thermotolerant S. cerevisiae KKU-VN8 exhibits a great potential for commercial-scale ethanol production in the future.
Subject(s)
Pichia/metabolism , Saccharomyces cerevisiae/metabolism , Ethanol/metabolism , Pichia/isolation & purification , Pichia/genetics , Pichia/chemistry , Asia, Southeastern , Saccharomyces cerevisiae/isolation & purification , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/chemistry , Sorghum/metabolism , Glucose/metabolism , Hot TemperatureABSTRACT
Two thermotolerant, ethanol-producing yeast cultures: THFY-4 and THFY-16 were isolated from 381 nature samples. THFY-4 can grow on 30% glucose plate at 51 ℃,while THFY-16 can grow on the same medium at 45℃.After preliminary ide ntification, THFY-4 was identified as Kluyveromyces sp. and THFY-16 belon gs to Saccharomyces genus. The ethanol fermentation experiment shows that T HFY-4 can only produce 4.88% (v/v) ethanol from 20% glucose after 60 hours, wh ile THFY-16 can produce 11.44% ethanol under the same condition. When using s accharified Canna edulis Ker wort as fermentation medium, 9.43%(v/v) ethanol we re produced from 16.1% glucose, which is 91.0% of the theoretical yield.