| Aiming at the high cost of artificially added carbon sources in the shrimp farming and biological floc farming models,this paper intends to isolate cellulase-producing bacteria from the tropical marine environment of Hainan,aiming to make full use of cheap natural fibers for future shrimp farming models.As an artificial carbon source,lay a foundation for bacteria.This article starts from the Prawn Farming Base in Haiwei Town,Changjiang Li Autonomous Region,Hainan Province,China,Prawn Farming Base in Huiwen Town,Wenchang City,Seagrass Bed Ecosystem Around Mangroves in Huiwen Town,Wenchang City,and Coconut Forest Seagrass Bed Ecological in Dongjiao Town,Wenchang The system collected 94 samples and a total of 2585 indigenous bacteria were isolated from it.After Congo red staining,97 strains of bacteria with cellulolytic ability were initially selected.Through 16S r DNA sequence alignment,97 strains belonged to 6 genera,including Bacillus,Microbulbifer,Vibrio,Pseudomonas,Tenaciculum,and Muricauda,and their proportions were 63.92%,10.31%,17.53%,6.19%,1.03%,1.03%.further The cellulose hydrolysis capacity(D/d)of these strains was measured.The results showed that the D/d of 58 strains of bacteria was between1.09±0.04～3.95±0.24;and the standard cellulose commercial enzyme(2.41U/g)was For reference,the WCHSL181223C58 24h culture supernatant had the highest enzyme content,reaching 3.14±0.22 U/g.The filter paper enzyme activity(FPase)measurement results showed that the best time to determine FPase for cellulase-producing strains was 24 hours in culture.WCHSL181223C57 showed the highest level of FPase of 2.325±0.061 U/m L.Antibiotic susceptibility testing results show that 82.14%of the strains are sensitive to chloramphenicol,and 28 cellulase-producing strains have a low antibiotic resistance index.The laboratory simulates the Litopenaeus vannamei farming system on a small scale,and selects strains adapted to the aquaculture environment from 28high-enzyme live strains(D/d≥2).The test results of high concentration(10~7CFU/m L)strains on Litopenaeus vannamei soaked showed that 26 strains of cellulase-producing strains were soaked for 7 days,and the shrimps grew normally.The analysis of the genetic stability of 26 cellulase-producing marine bacteria showed that the enzyme activities of all 20-generation strains of the tested bacteria were stable.Salinity tolerance screening test results show that 11 strains are suitable for freshwater or brackish water culture(0‰～10‰),11 strains are suitable for seawater culture(15‰～30‰),only 1 strain can adapt to In high-salt environment(30‰～40‰),3strains showed halophilicity.The results of the p H tolerance screening test showed that 9 strains showed acid resistance(p H5.0～6.0),15 strains grew well in a neutral environment(p H 7.0),and 2 strains showed alkali resistance(p H8.0～9.0),of which13 The strains have a wide range of acid and alkali resistance(p H5.0～9.0).According to the results of bagasse cellulase activity,the 26 strains of marine bacteria bagasse cellulase activity ranged from 0.072±0.079 to 4.14±2.276U/m L.Using bagasse as the sole carbon source to study the degradation effect of cellulase-producing marine bacteria,based on the analysis results of the 15-day bagasse decomposition rate,DJYL181224C18 bagasse decomposition rate was 63.81±0.027%,followed by strain WCHSL181223M15(48.57±0.123%).In summary,this paper has obtained cellulase-producing marine bacteria that are safe for farmed shrimp,sensitive to antibiotics,high genetic stability,a wide range of salinity and p H tolerance,and high bagasse decomposition rate.The shrimp breeding model,such as low-cost external carbon sources,has laid an important foundation. |
PDF Full Text Request