高效降解蛋白枯草芽孢杆菌的筛选及促建鲤生长的研究

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

【目的】从建鲤肠道分离并优选出了一株对蛋白具有强效降解力的菌株,探究其临床生产效果。【方法】使用牛奶平板进行筛选,经常规细菌学鉴定和16S rDNA序列分析确定A7菌株为枯草芽孢杆菌,通过临床饲喂试验探究其对建鲤促生长作用。【结果】A7菌株在牛奶平板上的水解圈直径可达27.5 mm,其最佳固体发酵条件为温度28°C、接种量5%(1.2×109 CFU/mL)、料水比1.0:1.2和发酵时间72 h。临床饲喂试验结果表明,饵料中添加0.5%、1.0%和1.5%的A7株菌粉均能促建鲤生长。其中,添加量为1.0%的试验组,鱼体增重率和蛋白利用率最高,饵料系数最低,与产品对照组和空白对照组相比,均达到了显著性差异(P<0.05)。此外,随A7株菌粉添菌量的增加,各试验组肝胰脏和肠道的蛋白酶及淀粉酶活力出现先增大后减小趋势,与产品对照组和空白对照组相比,添加1.0%的试验组增幅最大(P<0.05)。研究发现,试验组鱼肌肉中粗蛋白和粗脂肪含量较空白对照组也有明显的增减趋势(P<0.05)。【结论】饵料中添加A7株菌粉,可有效促进鱼的生长,降低饵料系数,提高肝胰脏和肠道的蛋白酶及淀粉酶活力,并提高鱼肌肉中的蛋白含量和降低脂肪含量。

[Objective] To obtain Bacillus subtilis A7 and explore its clinical use. [Methods] A7 was screened through milk plate and identified by conventional bacteriology and 16 S 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： temperature28℃, inoculation amount 5%（1.2×10^9 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 adecrease 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.