碳源对Bacillus cereus CZ氨肽酶产量及糖代谢酶活性的影响

Effects of Carbon Sources on Production of Leucine Aminopeptidase and Activities of Sugar Metabolic Enzymes Produced by Bacillus cereus CZ

摘要:

本文对Bacillus cereus CZ生产亮氨酸氨肽酶（LAP）进行了研究。结果表明，L-阿拉伯糖最利于LAP生产，D-半乳糖和乳糖也有较好效果，葡萄糖、麦芽糖、蔗糖或碳酸氢钠则强烈抑制LAP产生。L-阿拉伯糖和单糖混合、乳糖或半乳糖与葡萄糖混合均大大降低LAP产量。乳糖、葡萄糖有利于细胞生长。2%的乳糖、半乳糖或阿拉伯糖作为碳源，发酵48 h时LAP产量并没有达到最高。对于三种糖代谢酶，β-半乳糖苷酶受乳糖强烈诱导，D-半乳糖则强烈抑制该酶的活性，半乳糖激酶受D-半乳糖强烈诱导。L-阿拉伯糖异构酶受L-阿拉伯糖强烈诱导。当L-阿拉伯糖和半乳糖的浓度为4%时，LAP产量达到最高。胞外半乳糖激酶随D-半乳糖增加而降低，而胞内正好相反。L-阿拉伯糖异构酶活性随L-阿拉伯糖浓度增加而增加。当L-阿拉伯糖为4%时，LAP产量在发酵56 h达到最高，但在半乳糖为4%时，LAP产量随时间延长而增加。

Abstract:

Leucine aminopeptidase (LAP) produced by Bacillus cereus CZ was investigated in this study. Results indicated that L-arabinose was the best carbon source for producing LAP, followed by D-galactose and lactose, whereas glucose, maltose, sucrose and sodium bicarbonate obviously inhibited LAP production. The production of LAP was also reduced largely when L-arabinose was mixed with other simple sugars, or Lactose/ D-galactose was mixed with glucose. The mixture of lactose and glucose was the optimal carbon sources for cell growth.When using 2% lactose, D-galactose and L-arabinose as carbon sources, LAP activities did not reach the maximum values after 48 h fermentation. For the sugar metabolic enzymes, β-galactosidase can be strongly induced by lactose. L-Arabinose had certain induction effect, while D-galactose had a strong depression effect. Galactokinase was induced significantly by D-galactose, followed by L-arabinose and lactose. L-arabinoseisomerase was induced strongly by L-arabinose, moderately by other simple sugars and mixed sugars. LAP production reached the highest with 4% L-arabinose and D-galactose. Extracelluar galactokinase decreased with increasing the sugar concentration, but intracellular enzymes showed the reverse trend. L-arabinoseisomerase increased with increasing concentration of L-arabinose. LAP production reached the highest when fermentation for 56 h with 4% L-arabinose. However, its production increased continuously with fermentation time when 4% D-galactose was used.