The Breeding Of The Lactic Acid Producing Bacteria And The Research Of Its Fermentation Condition

The lactic acid was an important acid in the biology and had great applied value in the people's life. Especially in recent years, with the application of the poly L-lactic acid for the new material, the demand quantity of the lactic acid increased greatly. The lactic acid could divided to three isomers: L(+), D(-)and DL. Because only the L-lactic acid could metabolized in humans the research of the massive production of the L-lactic acid became a trend.This paper focused on the selection and identify of the L-lactic acid producing bacteria, breeding the strain and studying the fermentation substrate and cultivation condition of the mutant strain. The detailed contents were as followed:1. As the size of the clarity circle in the culture plate was the indicative index, 120 strains producing acid were obtained from 30 sample which collected from soil, verjuice et. Through the test of the glucose's decompose and examining the ingredients of the fermentation liquid by gas chromatography, 24 strains which were homo-lactic fermentation were selected. After repeat selection, examining the isomer of the production and the strains' stability, the stain named L110 was selected for further studied. Its yield could get 25g/L.2. According to the Bergery's Manual of Determinative Bacteriology(8th Edition),the strain was determined to be Lactobacillus casei L110 by the study of its colonial, cell morphology, physiochemical characteristics and fermentation speciality etc.3. The stain L110 was chosen as the start strain for mutagenic treatments with ultraviolet irradiation, N~+ implantation of low energy and endurance training of the lactic acid, after first and second selection, the mutant L110Z5-2 was selected. It showed better growth and yield characters than the L110.The average L-lactic acid yield was 65g/L which improved 1.8 times.4. The optimal fermentation medium and fermentation conditions of the...