摘要:
高压热杀菌处理(HPTS)下芽孢皮层肽聚糖水解是造成细菌芽孢死亡的重要原因,芽孢自身皮层裂解酶活力变化对皮层肽聚糖水解有直接影响。本文从枯草杆菌芽孢中提取了皮层裂解酶,先研究了磷酸钠浓度、pH、温度和压力对皮层裂解酶活力的影响,在此基础上研究了HPTS对该酶活力的影响。结果发现,皮层裂解酶的最适磷酸钠浓度为0.05 mol/L,当磷酸钠浓度为0.35 mol/L 时,皮层裂解酶活力较低;当pH为7时,皮层裂解酶活力最强,偏酸或偏碱性条件下,活力均有所降低;在4~44 ℃时皮层裂解酶均具活力,酶活变化无明显规律,但当温度升至68 ℃时皮层裂解酶基本失活;在150~530 MPa压力范围内,压力对皮层裂解酶活性基本无影响,然而HPTS处理时(530 MPa、68 ℃、15 min),皮层裂解酶基本失活,而皮层裂解酶是芽孢中唯一能特异性地水解皮层肽聚糖的酶,由此可推测HPTS处理下皮层肽聚糖发生了非酶水解。
Abstract:
The hydrolysis of spore’s cortical peptidoglycan under HPTS treatment was a critical reason for spore inactivation. However,the hydrolysis principle was still not clear. The activity change of spore’s cortex-lytic enzyme had direct effects on hydrolysis of cortical peptidoglycan. The cortex-lytic enzyme was extracted from Bacillus subtilis spores,and the effects of sodium phosphate concentration,pH values,temperature and pressure on the activity of extracted enzyme were studied firstly,which was a basis for further research on HPTS’s effects on the activity. It was found that the optimal concentration of sodium phosphate was 0.05 mol/L,and when the concentration was 0.35 mol/L,the enzyme activity was the lowest. The optimal pH for the enzyme was 7,and at acidic or alkaline conditions its activity decreased. At 4~44 ℃ the enzyme had activity with no obvious change rule,but when the temperature increased to 68 ℃ the enzyme lost basically its activity. At 150~530 MPa,the pressure had almost no effects on activity of the enzyme,but HPTS treatment(530 MPa,68 ℃,15 min)inactivated the cortex-lytic enzyme basically,and it was the only enzyme in the spore that could hydrolyze cortical peptidoglycan specially,which suggested that non-enzymatic hydrolysis of spore’s cortical peptidoglycan occurred under HPTS treatment.
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