Studies On The Fermentation Conditions And Induced Mutation Breeding Of The Bacillus Subtilis B68 Strain

The antagonistic strain Bacillus subtilis B68 was screened from banana plantation in Danzhou, Hainan province. It had a strong antagonism to the pathogen of banana crown rot. The aseptic filtrate of B68 can restrain the spores germinating, made the cell wall of the mycelium broken. All these indicate that the strain B68 has a wide potential to exploite to agriculture antibiotic.Seeing that B68 strain is a wild-type one ,the fermenting potency is rather low, it can't meet the requirement of industrious manufacture. This paper studied its fermentation conditions firstly, and then, taking B68 strain and Fusarium F4 as a starting strain and an indicative strain respectievely,used some physical and chemical factors to mutative breeding. The results of this paper as the following:1) the fermentation conditions of Bacillus subtilis B68 strain: Bacillus subtilis B68 was best growth in number six medium from 16 kinds media which were tested. It's aseptic filtrate can well control the pathogen of banana crown rot F4.the antagonism was 77.12percent, and only 0.33percent spores can germinate. From the primary screening for basic nutrients,it proved that the best carbon source was glucose, sucrose and amylum next; the best nitrogen source was yeast, peptone next.The initial pH of culture mendium, culture stage, culture temperature and so on had obvious influence to antibiotic. The medium with initial pH7.0, culturing 3 days, fermenting 48h at 28℃was best fermentation conditions of the B68 strain.2) After B68 strain was treated by different mutative factors, the results showed that they had different lethal effect on it. By mutative breeding and the initial screening menthod of culturing face to face on a plate, 28 high-yield strains were obtained.3) By fermenting 28 high-yield strains from the initial screeing in shaking flasks,12 ones of them were thought to be high-yield ones. Of which, UV ray mutation had 3 strains, U-28,U-43 and U-116. Compared with B68 strain, their inhibitory effects were improved 3.55%,4.37%,3.64%; DES mutation had 3 strains to,they were D-24,D-26,D-87. Their inhibitory effects were improved 4.22%,5.90%,3.83%; UV and DES...