Breeding Of L-lactic Acid Producer And Preliminary Research Of Fermentation Conditions

Lactic acid is one of the most widely used organic acids in the food industry and is a very common substrate for chemical synthesis. Recently, there has been an increased interest in lactate because it can be used as raw material for the production of biodegradable polymers with applications in medical (high resorption thread), pharmaceutical (low diffusion drug), and food industries (packaging). Now, production of lactic acid is achieved with a fermentation process using whey permeate or molasses as carbon source. Bacillus coagulans is an atypical strain for lactic acid production; the thermophile character of this strain proves that it is particularly adapted for industrial production of lactate without sterile conditions.In this paper we first breed an L-lactic acid bacteria B.coagulans through ultraviolet light. The mutant RS-UV-89 which L-lactic acid output is 6% higher than that of the original strain was obtained after being selected in the different plate such as the medium with high concentration of glucose, CaCO3-Bromocresol purple. And then through low-energy ion implantation on B.coagulans, we observed and counted the biological effects of the B.coagulans. We also research different energy and dose mutating effect on B.coagulans to make the fundaments for exploring the interaction between low-energy ions and complicated organisms further. At the same time by strain breeding one of high-yield mutant strain RS12-6C was obtained. RS 12-6C's output of lactic acid was increased by 20% than that of the parent strain.Through the preliminary research of cultivation condition of the mutant strain RS12-6C, the culturing conditions such as the optimal carbon and nitrogen source and their optimal concentration and so on, were determined. And the main factors of temperature and oxygen supply were studied deliberately, which provided the convenience for the next step research on fermentor.We also through 5L fermentor, B. coagulans RS12-6C was studied in batch and continuous mode to prove the real potentiality and the performance of this bacterium. The optimization of temperature, pH regulation, was performed since these factors are essential for lactic acid producers. First, an experimental design was developed to find the influence of optimize physical parameters (pH and oxygen supply). After that, continuous processes were performed to define the experimental domain conditions such as influence of carbon source optimal concentration and dilution rate.