Study On The Properties Of Biodegradable Bacteria With Antibiotic Tolerance

Agar is a marine bio-polysaccharide,the degradation product agaro-oligosaccharide has many biological activities,it has good economic value and application prospect.Screening high-efficiency and stress-resistant agar-degrading bacteria is an important step in the preparation of agaro-oligosaccharide.In the study,a strain of agar-degrading bacteria was screened from mangrove sediments in Fangchenggang City,Guangxi Zhuang Autonomous Region.It was identified by 16s rRNA,and some physiological and biochemical properties,strain resistance to some antibiotics,effects of different factors on the agarase production,and the conditions for producing agarase,and partial properties of the agarase.The main results are as follows:The strain was identified as Stenotrophomonas sp.by 16s rRNA,named Stenotrophomonas sp.N1,the preservation number was CCTCC NO:M 2019073.The strain was a Gram-negative bacterium,aerobic,salt-tolerant,could not decompose cellulose,and could not produce hydrogen sulfide.The strain was highly resistant to antibiotics and could grow normally on nutrient agar medium containing norfloxacin,sulfamethoxazole,and tetracycline(concentrations of 1000 mg/L).The effects of single factor conditions such as temperature,initial pH,inoculation age,inoculation quantity and culture time on agarase produced by strain Stenotrophomonas sp.N1 were determined,the suitable enzyme production conditions for the strain are as follows:incubation temperature was 40 ?,initial pH of the medium was 7.5,inoculation agewas 10 h,inoculation volume was 10%,and incubation time was 48 h.According to the results of single factor experiments,the agarase conditions of the strains were optimized by orthogonal test.The optimized conditions of enzyme production are as follows:incubation temperature was 40 ?,initial pH of the medium was 7.5,inoculation volume was 12%,and incubation time was 48 h.When the enzyme production conditions were optimized,the low concentration of norfloxacin,sulfamethoxazole or tetracycline had little effect on the enzyme activity.When the concentration of a single antibiotic was 300 mg/L,the enzyme activity decreased by 17.47-18.03%,when the concentration of an antibiotic was greater than 500 mg/L,the enzyme activity decreased significantly.The agarase produced by the strain Stenotrophomonas sp.N1 was extracellular agarase-(3,it could degrade agar into neoagarobiose.About theagarase,the optimal catalytic temperature was 35 ?,it had good thermal stability in the temperature range of 25-45 ?,and could maintain relative enzyme activity of more than 70%.The optimal catalytic pH was 7.0,and the strain had good pH stability in the pH range of 5-8,and could maintain relative enzyme activity of more than 70%.The agarase activity was the highest when the concentration of agar was 0.3%.The agarase had good degradability to carrageenan,but it was difficult to degrade alginate and chitosan.