Screening and identification of marine alginate lyase-producing bacteria and optimization of enzyme production conditions

Alginate lyases are mostly derived from marine bacteria with unique living environments. Using sodium alginate as the sole carbon source, a strain with high-yield alginate lyase from 56 strains of marine bacteria was screened using primary screening by transparent circle method and rescreening for enzyme activity determination by 3,5-dinitrosalicylic acid (DNS) method. The screened strain was identified by morphological observation, physiological and biochemical tests and 16S rDNA gene sequence analysis, and using alginate lyase activity as the response value, the fermentation conditions for the screened strain for alginate lyase production was optimized by Plackett-Burman experiment combined with Box-Behnken response surface method. The results showed that the strain I14 with high-yield alginate lyase was obtained, and it was identified as Bacillus velezensis, and the optimum fermentation conditions for alginate lyase production by the strain I14 were determined as follows: sodium alginate addition 5 g/L, soluble starch addition 5 g/L, yeast powder addition 4.30 g/L, peptone addition 10 g/L, NaCl addition 30 g/L, CaCl₂ addition 0.30 g/L, initial pH 6.0, fermentation temperature 35 ℃, time 24 h, and liquid loading volume 30 ml/100 ml. Under these optimal conditions, the activity of alginate lyase reached 81.29 U/ml, which was 4.76 times that of before optimization. This study provided a new strain option for the development and utilization of alginate lyases, and expanded the application of strain I14 in food and biological fields such as degradation of alginate and production of polysaccharide lyases.