Expression Plantaricin In S. Cerevisiae To Prevent Bacterial Contamination Of Bio-Ethanol Fermentation

With rapid exploitation of fossil fuels, the environmental problems such as air pollution, global warming, and haze weather have been worse and worse, and people’s demand for clean and renewable energy resources has been more and more urgent. In the meantime, because of its environmental protection, high energy efficiency, and renewable advantages, bio-ethanol is followed with interest by scientists from various countries.Currently, the studys around bio-ethanol’s non-food material use, ethanol tolerance of yeast, and bacterial contamination prevention have been widely researched. It is noteworthy that due to equipment leaks, seed infection and other problems which are difficult to avoid, bacterial contamination often occurs in industrial bio-ethanol fermentation. If this problem can’t be effectively controlled, it will seriously affect the ethanol production, and therefore lead to enormous economic loss. Previous studies had showed that the lactic acid was the major contamination bacterium in bio-ethanol fermentation, owing to its resistance to both low pH and ethanol and its high proliferation rate. Lactic acid bacteria’s negative influences will cause adverse effect on the growth of yeast and the ethanol production, as a result of its nutrients consumption, growth environment occupying and lactic acid producing, etc. Based on its physiological and biochemical characteristics, people worked out a series of methods to control lactic acid bacteria contamination, and the most widely used way is antibiotics method. Antibiotics have the advantage of high efficiency and low price, while it’s also provided with the disadvantages such as drug residues and drug resistance. As people pay more and more attention to environmental issues, finding environment friendly and antibiotic alternative method to prevent and control the bacterial contamination is very imminent.This topic took use of plantaricin to control the lactic acid bacteria contamination during the fermentation of Saccharomyces cerevisiae. The experiment selected Lactobacillus plantarum ATCCBAA-793 as the producing strain of plantaricin, and extracted its culture supernatant fluid as crude plantaricin product. The experiment took Saccharomyces cerevisiae S288c as fermentation strain, and took Lactobacillus plantarum ATCC 8014 as contamination strain. Control group, contamination group and plantaricin treatment group were set to explore the antibacterial effect of plantaricin via measuring the quantity of ATCC 8014 and S288C, and the ethanol content in terminal fermentation stage. The result showed that the plantaricin had effective inhibition to ATCC 8014. Moreover, in the plantaricin treatment group, both the quantity of S288c and the ethanol content were restored to normal level (compared with the control group, P>0.05; compared with contamination group, P<0.05). In addition, this topic added plantaricin during the initial stage of S288c cultivation, and found plantaricin was non-toxic to Saccharomyces cerevisiae, according to its safety by measuring the quantity of S288C during the fermentation and the production of ethanol during the terminal fermentation.This research took InvScI as the host, and transferred three kinds of plantaricin encoding gene, including plantricinA (plnA), plantricinE (plnE) and plantricinF (plnF), into it through pYES2 respectively, which constructed engineering bacteria with the secretory expression of target fragment. They were named as InvScI-plnAN InvScI-plnEN InvScI-plnF. The experiment induced InvScI-plnA、InvScI-plnE、InvScI-plnF to express plnA, plnE and plnF, and explored the antibacterial activity. Their supernatant cultures showed effective antibacterial activity to ATCC8014...