Development And Biological Application Of Multifunctional Microbial Preparations For Shrimp Farming

The high-density and intensive shrimp farming has brought huge economic benefits,but it has also caused a series of problems such as deterioration of water quality and frequent occurrence of diseases.Under the background of the full implementation of“antibiotic-free farming”,microbial preparations have been widely used in shrimp farming because of their advantages of greenness,pollution-free and no drug resistance.This paper intends to optimize the multi-functional microecological strain through nitrite degradation experiment and anti-micrococcus luteus experiment,optimize its fermentation process and explore its fermentation rules,and apply the product to small-scale cultivation of Penaeus vannamei.The mechanism of microbial preparation was discussed by studying the biological culture effect and the species diversity and community structure of the bacterial community in the culture system,providing theoretical basis and data support for the further development and utilization of microbial preparation.A multifunctional microecological strain was screened by nitrite degradation experiment and resistance to Micrococcus luteus.Using 15 strains of bacteria preserved in the laboratory as the starting strains,the nitrite degradation screening experiment was carried out,and 9 strains of nitrite efficient degrading bacteria were obtained.After screening,a multifunctional strain FS051 with both nitrite degradation ability and resistance to Micrococcus luteus was finally obtained.The morphological observation,physiological and biochemical identification,and 16 S r DNA molecular biology identification of FS051 were carried out to determine its taxonomic status as Bacillus licheniforms.The optimal fermentation process parameters of FS051 strain were determined through the condition optimization experiment.The optimal fermentation medium of FS051 strain was obtained by single factor experiment combined with response surface optimization: starch 10.59 g/L,peptone 7.08 g/L,urea 0.088 g/L,Ca Cl2 0.2 g/L;optimal fermentation conditions: inoculum volume 2.5%,the temperature was 33℃,the rotation speed was 180 r/min,the initial p H was 7.0,the liquid volume was 40 m L(250 m LΔ),the final fermentation titer was 9845.65 IU/m L,and the number of viable bacteria in the fermentation broth was 10.39×109 CFU/m L.Based on the classical fermentation kinetics and the optimization equation of Origin2018 software,the fermentation kinetics model of bacterial growth,substrate consumption and product generation during the fermentation process of strain FS051 was constructed.(1)The fermentation process model of strain FS051 constructed based on the classical kinetic equation:a bacterial cell dynamic model:(?)a product generation dynamic model:(?)a matrix consumption dynamic model:(?)(2)The fermentation process model of strain FS051 constructed based on the Origin2018 software optimization equation:a bacterial cell dynamic model:(?)a product generation dynamic model:(?)a matrix consumption dynamic model:(?)To explore the biological effects of bacterial preparation product FS051 on culture of Penaeus vannamei and the effects of bacterial community and diversity in culture water body and intestinal tract of Penaeus vannamei by high-throughput sequencing technology.(1)The addition of the product significantly reduced p H,salinity,ammonia nitrogen content,nitrite nitrogen content and the number of pathogenic vibrio in aquaculture water,and significantly promoted the growth of penaeus prawn.(2)The addition of the products increased the diversity and richness of the bacteria in the aquaculture water body and the intestinal bacteria,and changed the bacterial community structure,especially in the aquaculture water body.(3)The relative abundance of beneficial bacteria such as Gemmobacter,Paracoccus and Bacillus increased with the addition of the products.The relative abundance of Flavobacterium,a potential pathogen,in shrimp intestines decreased.(4)The addition of the product changed the dominant bacterial structure of aquaculture water body and shrimp intestine.In water samples,the dominant bacteria in control group and prevention group were all Aurantimicrobium,but the relative abundance of prevention group was lower than control group.In the intestinal samples of shrimp,the dominant bacteria in the control group were Gemmobacter and Fluviicola,and the dominant bacteria in the prevention group were Aurantimicrobium.