鲁氏接合酵母对酱油中氨基甲酸乙酯前体物的代谢

Metabolism of ethyl carbamate precursors in soy sauce by Zygosaccharomyces rouxii ZQ02

【目的】研究鲁氏接合酵母氮源代谢特性,确定鲁氏接合酵母氮源代谢与酱油中氨基甲酸乙酯前体物瓜氨酸和尿素积累的关系。【方法】通过单一氮源培养、偏好型氮源培养和盐胁迫培养,检测不同条件下鲁氏接合酵母对精氨酸、瓜氨酸和尿素的代谢能力。【结果】通过对鲁氏接合酵母氨基酸利用能力的分析,确定了甘氨酸、丙氨酸和天冬酰胺3种氨基酸为鲁氏接合酵母的偏好型氮源。在偏好型氮源存在时,鲁氏接合酵母对尿素和瓜氨酸的利用并不受到抑制,丙氨酸和甘氨酸还能够促进对二者的利用。鲁氏接合酵母在单一氮源培养条件下不会降解精氨酸而积累尿素和瓜氨酸,反而可以大量利用氨基甲酸乙酯的前体物尿素和瓜氨酸。但在盐胁迫下,鲁氏接合酵母利用尿素和瓜氨酸受到阻遏,从而造成酱油中氨基甲酸乙酯前体物不能被充分利用而积累。【结论】盐胁迫阻遏了鲁氏接合酵母对瓜氨酸和尿素的利用,从而造成酱油发酵过程中耐盐细菌所产生的氨基甲酸乙酯前体物的积累。

[Objective] To study nitrogen metabolism of Zygosaccharomyces rouxii and its relationship with the formation of soy sauce ethyl carbamate precursors. [Methods] Z. rouxii ZQ02 was cultivated with single source of nitrogen, preferred nitrogen sources or under salt stress, to investigate its ability of using arginine, citrulline and urea.[Results] Alanine, glycine and asparaginate were confirmed to be the preferred nitrogen sources of Z. rouxii ZQ02.Addition of preferred nitrogen sources did not inhibit the use of urea and citrulline, on the contrary, the consumption of urea and citrulline by Z. rouxii ZQ02 was stimulated with the addition of alanine and glycine. Z. rouxii ZQ02 did not accumulate any citrulline and urea from degradation of arginine. Urea and citrulline were used by Z. rouxii ZQ02 in the medium with single source of nitrogen. However, use of citrulline and urea by Z. rouxii ZQ02 was strongly inhibited under saline stress, resulting in the incomplete use of ethyl carbamate precursors. [Conclusion] Use of citrulline and urea by Z. rouxii ZQ02 was strongly inhibited under high salt stress, resulting in the accumulation of ethyl carbamate precursors produced by other microorganisms during soy sauce fermentation.