The Inhibiton And Mechanism Of Bacillus Subtilis On Rotting Fungi On Postharvest Mulberry Fruit

Mulberry fruit is the fruit of the moraceae morus perennial woody plant mulberry, a kind of polythalamic fruit, taste sweet and sour. Mulberry fruit contained with a variety of functional ingredients, such as resveratrol, anthocyanins and rutin, etc, and have many good ability such as anti-cancer,anti-aging,hypoglycemic action, antioxidant, anti-ulcer, anti-virus. However,mulberry belong to the berries fruit, with high water content, extremely thin skin, soft and succulent,Muberry fruit’s mature period time in high temperature season, so when keep it at room temperature for 1-2 d,it will began to rot. At present, the fruit fresh keeping used more chemical preservation and physical preservation, as people care more about health,safety, environmental protection, biological preservation has an extremely prospects for development. For the research of biological preservation on mulberry fruit,this paper studied the antagonism microbes of the main caused rot fungi on mulberry fruit.We particular discussed Bacillus subtilis’ s antibacterial material and antagonism mechanism, in hope of offering theoretical basis and technical support to mulberry microbial preservation,the results were as follows:1、Screening of good antagonism microbial to mulberry rot fungi. Respectively by Pichia pastoris, Sporidiobolus pararoses, Bacillus subtilis, Trichoderma harzianum four strains, use plate culture method, according to the inhibition rate,It turned out that Bacillus subtilis has a very good function. After that,we had a reaserch on Bacillus subtilis’ s bacteriostatic effect and stability of bacteria suspension,fermented supernatant, fermentation filtrate.Results showed that Bacillus subtilis’ s suspension has the best bacteriostatic effect, the inhibition rate on Sclerotinia sclerotiorum. GA and Alternaria sp. GE can reach 77.88% and 80.61%,after co-cultured 8d, it still have good inhibitory effect.In addition Bacillus subtilis’ s antibacterial substances mainly exists in cells, the bacteria suspension has the highest content.2、Bacillus subtilis’ s antibacterial material separation, purification, and properties.Separate Bacillus subtilis’ s antibacterial material from centrifugal fermented liquid, adopting acid sinking and alcohol extraction process,via Sephadex G-100 purification, it devide into p1, p2, p3 three components. Antibacterial experiments on the PDA plate showed that p2 components has good bacteriostatic activity,combined with ultraviolet spectrum, infrared spectrum, and the analysis of theMALDI-TOF-MS/MS, the results show that the antibacterial substance is Fenycin,which a kind of lipopeptide.The lipopeptide have good temperature stability, after treated by 80℃for 30 min, it is also have a good antibacterial effect,beside the antibacterial material has good acid stability, with high effection in partial acid,neutral environment,insensitive with proteinase K.3、Research on the machanism of Bacillus subtilis’ s lipopeptide of Fengycin.Through microscopic observation, the hyphae and spores of rot fungus Alternaria sp. GE and Sclerotinia sclerotiorum. GA became rupture after antibacterial material treatment.Bacillus subtilis inhibit the growth of the rot fungi by secrete antimicrobial substances manifest by nutrition and space competition. In addition, the POD enzyme activity of mulberry is significantly increased, and PPO enzyme activity reduced after dealing with the Bacillus subtilis bacteria suspension.