两株芽孢杆菌降解羽毛比较及抗氧化肽分离

Comparison of feather degradation by two Bacillus strains and separation of antioxidant peptides

枯草芽孢杆菌UMU4和短小芽孢杆菌SCU11是四川省分子生物学及生物技术重点实验室分离的野生菌株经诱变获得的胞外蛋白酶高产菌株,其分泌的蛋白酶在蛋白废弃物处理方面具有良好的应用前景.为了从这两株芽孢杆菌中筛选出高效利用羽毛的最优菌株,将UMU4和SCU11分别接种到羽毛培养基中并持续发酵6 d,通过每天测试羽毛降解率、可溶性多肽含量、氨基酸含量、蛋白酶活及抗氧化活性等指标来评价这两株菌对羽毛的降解能力.结果发现SCU11能更高效地利用羽毛,其羽毛降解率是UMU4的1.2倍,第5天时约有65%的羽毛转化为可溶性肽和氨基酸;SCU11发酵液的ABTS自由基清除率和还原力均在第3天达到最大值,且显著高于UMU4羽毛发酵液的抗氧化活性;SCU11在第5天所产角蛋白酶和碱性蛋白酶的活性分别是UMU4的1.6和1.2倍.在此基础上,将来自于SCU11的羽毛降解产物经HCl沉淀和疏水层析获得了4个抗氧化肽组分,其中组分F3的抗氧化活性最高.本研究表明芽孢杆菌SCU11较之UMU4具有更高的产酶活性及更强的羽毛降解能力,结果可为家禽羽毛的资源化应用奠定基础.

In our previous study, Bacillus subtilis UMU4 and B. pumilus SCU11 were mutated with a high protease activity gene from wild-type strain. The proteases produced by these two strains showed good prospects in protein waste utilization. To screen the optimal strain for degrading feather among these two strains, SCU11 and UMU4 were inoculated into feather fermentation medium. The feather degradation rate, soluble peptide content, amino acid content, protease activity, and antioxidant activity were measured daily. It was found that the strain SCU11 could utilize the feather more effectively. Its feather degradation rate was about 1.2 times higher than that of UMU4. On day 5, about 65% of feather was degraded into soluble peptides. The 2,2＇-azino-bis（3-ethylbenzothiazoline-6-sulphonic acid）（ABTS） radical scavenging rate and reducing power of the fermentation broth with SCU 11 reached the maximal values on day 3, which were significantly higher than those of the fermentation broth with UMU4 strain. The activity of keratinase and alkaline protease produced by the strain SCU11 on day 5 was 1.6 and 1.2 times higher than those of UMU4. Furthermore, four antioxidant peptide fragments were separated from the feather degradation products of SCU11 through hydrochloric acid precipitation and hydrophobic chromatography separation. Among these fragments, F3 showed the strongest antioxidant activity. These results indicate the higher enzyme activity and greater capability of the strain SCU11 in feather degradation. The present study lays foundation for effective utilization of feather by biodegradation.