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Study on Screening & Fermentation of L-lactic Acid Bacteria on the Basis of Distillate of VHG Ethanol Fermentation from Corn

Author: ShiKongQuan
Tutor: ShiGuiYang
School: Jiangnan University
Course: Fermentation Engineering
Keywords: L- lactic acid Hawaii Enterococcus Thick mash alcoholic fermentation Corn distillers grains
CLC: TS261.11
Type: Master's thesis
Year: 2006
Downloads: 206
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Abstract

With the growing energy crisis, fossil fuels dwindling, leading to rising international crude oil prices in April 2006 is a breakthrough in the 75 U.S. dollars / barrel. Fuel ethanol as a clean energy alternative to fossil fuels, is currently a hot research topic in the international. For the production of fuel alcohol, how to reduce the cost of production is needed to solve a key. Paper as a starting point, the alcoholic fermentation-generation L-lactic acid process has been studied in order to achieve not only to solve the lees the pollution problem in the production of alcohol, while reducing the purpose of alcohol and L-lactic acid production costs, production and lay the foundation for subsequent amplification . Through the sample separation, customize filters to obtain an L-lactic acid bacteria, the optical purity of the testing showed that the lactic acid product of L-lactic acid content of 94.8%. Further initial carbon, nitrogen fermentation performance test, the strain and strain phenotype, physiological and biochemical characteristics combined with 16S rDNA sequence alignment to determine the strain Hawaii enterococci (Enterococcus hawaiiensis), tentatively named E. hawaiiensis WXS being no Hawaii Enterococcus publicly reported in the literature for the fermentative production of L-lactic acid. The use of chemical mutagen NTG E. hawaiiensis WXS repeated mutagenic treatment, get a good acid production strains E. hawaiiensis WXS58 of. Further investigated E. hawaiiensis WXS58 medium with glucose as carbon source in the fermentation performance, determine the optimum fermentation temperature of 34 ° C, suitable for seed age for 14-18 h, 3% of the optimum inoculum size, medium The optimum initial pH 6.0, in the early stage of fermentation, the amount of aerobic incubation of L-lactic acid generated better role in promoting. Fermentation medium was optimized by orthogonal experiment to determine the best fermentation medium: peptone 1%, yeast extract 1%, the NA ₂ HPO ₄ 0.15%, MgSO4 0.02%, in the medium after 48 h of fermentation, the fermentation broth L-lactic acid production reached 56 g / L. E. hawaiiensis WXS58 lees matrix domesticated strains were able to grow well in the supernatant of corn thick mash lees. Alcohol by examining the relationship between thick mash fermentation and L-lactic acid fermentation to determine the balance between the alcoholic fermentation and L-lactic acid fermentation: alcoholic fermentation to the end of the 36-40 h in advance, then mash Alcohol 12 %, lees directly after solid-liquid separation serum sugar at 70-80 g / L, after appropriate treatment for L-lactic acid fermentation. L-lactic acid fermentation of corn the thick mash lees serum matrix 7 L fermenter, 15 L tank small pilot plant. 7 L tank, fermentation initial glucose 67 g / L after 36 h of fermentation, the fermentation broth L-lactic acid production reached 52 g / L residual sugar 7 g / L, sugar and acid conversion rate of 86.7%; 15 L tank initial glucose 87 g / L after 48 h of fermentation, L-lactic acid production reached 68 g / L of sugar and acid conversion was 89.5%. 15 L tank, the maximum rate of formation of L-lactic acid in 12 h, to achieve a 2.86 g / L · h, the maximum rate of consumption of sugar in the lees 17.7 h, reaches 3.55 g / L · h. The economic costs of preliminary accounting, compared to separate the alcoholic fermentation, alcohol gravity fermentation process of co-L-lactic acid can increase the profit of 814 yuan / ton lees supernatant.

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