Sweet sorghum juice supplemented with 0.5% ammonium sulphate was used as a substrate for ethanol production by Saccharomyces cerevisiae TISTR 5048. In batch fermentation, kinetic parameters for ethanol production depended on initial cell and sugar concentrations. The optimum initial cell and sugar concentrations in the batch fermentation were 1 · 10 8 cells ml -1 and 24°Bx respectively. At these conditions, ethanol concentration produced (P), yield (Y ps ) and productivity (Q p ) were 100 g l -1 , 0.42 g g -1 and 1.67 g l -1 h -1 respectively. In fed-batch fermentation, the optimum substrate feeding strategy for ethanol production at the initial sugar concentration of 24°Bx was one-time substrate feeding, where P, Y ps and Q p were 120 g l -1 , 0.48 g g -1 and 1.11 g l -1 h -1 respectively. These findings suggest that fed-batch fermentation improves the efficiency of ethanol production in terms of ethanol concentration and product yield.
Problem statement:The prime objective in breeding selection process of drought-tolerant sugarcane is to identify the correlating marker, which could lead to rapid screening for drought-tolerant cultivars. In this study, we have reported an unknown 18-kDa protein (p18) along with other stress-inducible proteins to be highly expressed in sugarcane leaves under drought stress condition. Approach: The 2D-PAGE patterns of proteins were compared between those expressed in drought-tolerance K86-161 and drought-susceptible Khon Kaen 1 cultivars. The interested proteins were identified by mass spectrometry. The correlation between p18 expression and drought tolerance was verified in additional 4 sugarcane cultivars using ELISA and western blotting. Two physiological indexes, Chlorophyll content and SOD activity were also evaluated. Results: Mass spectrometry and comparison with known sequences in the database reveal that the proteins expressed only in stressed K86-161 are serine protease inhibitor and the one similar to replication protein A1. A group of proteins up-regulated in K86-161 are SAdenosylmethionine decarboxylase proenzyme (SAM), ubiquitin and p18. From ELISA and western blotting analysis, we found that p18 expressed in drought-tolerant sugarcane cultivars had higher binding specificity to antibody than that in drought-susceptible sugarcane cultivars. Two physiological indexes showed higher levels in drought-tolerant than those in drought susceptible sugarcanes. Conclusion: These high levels of chlorophyll and SOD are in agreement with a high level of p18 expression in droughttolerant sugarcanes. It is likely that an accumulation of p18 is a response to water deficit. In conclusion, p18 might be a good candidate for development as a marker in drought-tolerant plants.
Optimization of three parameters: agitation rate (A; 100, 200 and 300 rpm), aeration rate (B; 0.5, 1.5 and 2.5 vvm) and aeration timing (C; 2, 4 and 6 h), for ethanol production from sweet sorghum juice under very high gravity (VHG, 290 g L−1 of total sugar) conditions by Saccharomyces cerevisiae NP 01 was attempted using an L9 (34) orthogonal array design. The fermentation was carried out at 30 °C in a 2-L bioreactor and the initial yeast cell concentration was approximately 2 × 107 cells mL−1. The results showed that the optimum condition for ethanol fermentation should be A2B3C2 corresponding to agitation rate, 200 rpm; aeration rate, 2.5 vvm and aeration timing, 4 h. The verification experiments under the optimum condition clearly indicated that the aeration and agitation strategies improved ethanol production. The ethanol concentration (P), productivity (Qp) and ethanol yield (Yp/s) were 132.82 ± 1.06 g L−1, 2.55 ± 0.00 g L−1h−1 and 0.50 ± 0.00, respectively. Under the same condition without aeration (agitation rate at 200 rpm), P and Qp were only 118.02 ± 1.19 g L−1 and 2.19 ± 0.04 g L−1h−1, respectively while Yp/s was not different from that under the optimum condition.
Optimization of four parameters, i.e., zinc (Zn 2+ ), magnesium (Mg 2+ ), manganese (Mn 2+ ) and yeast extract for bioethanol production from sweet sorghum juice by Saccharomyces cerevisiae NP 01 under very high gravity (VHG, 270 g·L , respectively.
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