Primary Study On Indentification, Culture And Antimicrobial Activity Of Fermentation Broth Of Endophytic Actinomycetes Y₁₂ From Tobaccos

With the endophytic actinomycetes Y12 separated by professor Tan Zhoujin's Study Group from Hunan University of Chinese Medicine as the study subject, the author make a series of experiments on strain identification, optimal fermentation condition and the fermentation product's antimicrobial activity and stability. The results are as follows:1. According to morphological, cultural characteristics, physiological and biochemical characteristics and 16SrRNA sequence analysis, the strain Y12 was similar to streptomyces albogriseolus.2. Through a series of orthogonal experiments on Y12 including the selection and components of the fermentation medium and the optimal fermentation conditions, it is determined that the optimal fermentation medium was:1.5% soybean flour,1.5% peptone,1.5% glucose,1.5% soluble starch,0.05% MgSO4·7H2O,0.25%(NH4)SO4, 0.4% NaCl,0.1% KH2PO4 and 0.5% CaCO3. The optimal fermentation conditions were:optimal pH was 7.5, optimal fermentation temperature was 30℃, optimal fermentation time was 72h. It was observed from the experiments that the diameters of inhibition zones increased by 44.9% under such optimized conditions.3. It is indicated in the inhibition tests that the fermentation broth of strain Y12 against Escherichia coli, Staphylococcus aureus, Ralstonia solanacoarum, and Bacillus subtilis had obvious inhibitive effect, the diameters of inhibition zones were 28.1mm,29.2mm,22.8mm and 20.3mm respectively. The antimicrobial activity of the fermentation broth had no obvious changes when strain Y12 was sucessively cultivated 10 generations; and is stable to generations.4. The results of stability study on Y12's fermentation product suggested that it is stable to heat, with the activity ratio only decreasing by 3.01%,11.7%, and 21.5% when heated by 60℃,90℃and 100℃for 30 minutes respectively; The fermentation product is also stable to ultraviolet radiations and acid environment. The activity ratio keeps at 90.8% when radiated by the ultraviolet for 7 hours from the 30cm distance and declines by 9.08% with the pH at 4; however, when situated under the alkaline environments, its activity ratio will decrease evidently, with no activity when the pH reaching 11. Besides, its stability will also decrease with time going on under room temperature, with the activity ratio keeping at only 59.7% after 8 days. It is concluded heat, ultraviolet radiations and acid environment have little effect on the stability of Y12's fermentation broth while the storage time under room temperature influences the stability considerably.