| With the intensive development pattern of mariculture industry becoming more and more widespread, water pollution problem is increasingly serious, in which ammonia nitrogen level has been the major restrictive factor. Microecologics has been widely applied to improve water quality in aquaculture. Probiotics has two main functions, namely, improving water quality in aquaculture ponds and antagonizing pathogens. Studies have shown that the Bacillus can improve water quality by reducing the ammonia nitrogen and nitrate content effectively. Besides, as a kind of probiotic bacteria, bacillus can inhibit pathogenic bacteria to improve the water ecological environment.This study aims to develop immobilized composite bacillus microecologics suitable for mariculture, in order to solve the problem of high ammonia nitrogen content in mariculture.Ammonia nitrogen removing Bacillus has been screened and compared with the Bacillus from ACCC in ammonia nitrogen degradation rate, ammonia oxidase (amoA) and lactonase (AiiA) gene PCR under the same experimental conditions. The experimental results showed that the ammonia nitrogen degradation rate of A4 strain is the highest which reached 73.54% with the inoculum dosage of 2%, decreasing the ammonia nitrogen value from 25 mg/L to 5.73 mg/L. AiiA lactonase gene has been amplified and sequenced from Al strain by PCR, Preliminarily determines the Al strain carried within the AiiA esterase gene, have certain which preliminarily determines antibacterial potential of Al by the degradation of quorum sensing signal molecules AHL produced by pathogenic bacteria. The AHL degradation function of AiiA lactone enzyme in A1 has been verified quantitatively by method of ONPG reaction with the use of AHL indicating bacteria JZA1.The effect of ammonia nitrogen degradation of A4 strain immobilized by different carriers and the influence of superfine grinding processing of different carriers have been investigated. The experimental results showed that ammonia nitrogen removal effect of A4 immobilized by rice husk powder without superfine grinding is the best, with the removal rate reaching 82.92% for 25 mg/L initial ammonia nitrogen content in the inoculum dosage of 2%. The second highest is talcum powder without superfine grinding, reaching 81.30%. The ammonia nitrogen removal rate of A4 immobilized with corn cob powder after superfine grinding was 60.12%.The ammonia nitrogen removal efficiency of single bacterium agent immobilized with corn cob powder, rice husk powder and talcum powder in 5L open seawater environment has been investigated. The results showed that ammonia nitrogen degradation effect of microecologics in aeration conditions was much better. The ammonia nitrogen degradation effect of A4 immobilized on corn cob powder or rice hull powder was significantly higher than talcum powder.1% A4 immobilized with corn cob powder reduced ammonia nitrogen concentration from 25 mg/L to 11.17 mg/L within 96 h, with the degradation rate reaching 55.31%. The degradation rate of rice hull powder immobilized group was 55.45%.Corn cob powder has been chosen for the preparation of composite immobilized probiotics product. Four different kinds of corn cob powder immobilized compound bacterium agent products were prepared by the method of freeze drying, another compound bacterium agent products was prepared by natural drying with the same blending ratio. Each compound bacterium agent consisted of W, Al and A4, mixed ratio for carrier and bacteria liquid was 1:3. The experimental results showed that the effect of group 4 was the best (centrifugal liquid fermentation bacteria immobilized by super corn cob powder added with skim milk powder), reaching the highest ammonia nitrogen degradation rate at 70.87%, reduced the ammonia nitrogen concentration from 10 mg/L to 2.91 mg/L within 96 h in 5 L seawater system with the dosage of 10 g, which is significantly better than Baile commodity control group (P<0.05). |
PDF Full Text Request