Screening of high effective protein-degrading Bacillus subtilis and study on promotion to Jian carp growth

Abstract:

[Objective] To obtain Bacillus subtilis A7 and explore its clinical use. [Methods] A7 was screened through milk plate and identified by conventional bacteriology and 16S rDNA. Growth promoting effect on Jian carp was explored via clinical feeding experiments. [Results] Diameter of protein hydrolysis circle was 27.5 mm. The optimal solid fermentation conditions were: temperature 28 °C, inoculation amount 5% (1.2×109 CFU/mL), ratio of material to water 1.0:1.2, fermentation time 72 h. Diets with 0.5%, 1.0%, 1.5% A7 could promote Jian carp growth, and 1.0% A7 added displayed the highest weight gain and protein efficiency, and the lowest feed coefficient, difference was significant comparing with product group and blank group (P<0.05). With increasing dosage of A7, protease and amylase activity in hepatopancreas and intestine of all test groups increased first, then decreased, and compared with product group and blank group, 1.0% added was also the best (P<0.05). Besides, fish fed with A7 had obvious trend of an increase content in crude protein and a decrease in crude fat comparing with blank group (P<0.05). [Conclusion] Fish baits with A7 can promote growth, reduce feed coefficient, increase protease and amylase activity, and improve fish flavor.

Key words:Bacillus subtilis, Protein degradation, Weight gain, Jian carp