高温大曲中曲皮和曲心的理化指标、微生物多样性和挥发性物质研究

Physicochemical Indicators, Microbial Diversity, and Volatile Substances in the Qupi and Quxin of High-temperature Daqu

摘要:

【目的】探究高温大曲中曲皮和曲心的理化指标、微生物多样性和挥发性物质。【方法】采用高通量测序技术联合顶空固相微萃取-气相色谱-质谱联用技术（HS-SPME-GC-MS）等对3种大曲的曲皮和曲心这2个部位的微生物群落多样性、理化指标及挥发性物质之间的差异性进行研究。【结果】在理化指标方面，3种大曲的曲皮水分质量分数显著低于曲心（P<0.05），其中白曲曲皮（WP）的水分质量分数最低，黄曲曲心（YX）水分质量分数最高；曲皮、曲心的酸度大小依次为：黑曲曲心（BX）>YX>黑曲曲皮（BP）>白曲曲心（WX）>黄曲曲皮（YP）>WP。高通量测序结果表明：Firmicutes、Proteobacteria为大曲的优势细菌门，Ascomycota为优势真菌门；在属水平上，BP、BX、YX以Pseudomonas_E为主要优势细菌属；WP以Blastococcus为主要优势细菌属；WX以Scopulibacillus为主要优势细菌属；所有样品中，以Thermomyces为主要优势真菌属，但其相对丰度存在一定差异，且酱香型高温大曲中曲皮的微生物多样性优于曲心。冗余分析（redundancy analysis，RDA）结果表明：WP与水分质量分数和温度呈正相关，YX、BX与酸度呈正相关，且曲皮、曲心的微生态环境差异是导致其微生物群落结构差异的重要原因之一。大曲中曲皮、曲心的76种挥发性物质的定量分析结果表明：在酯类物质中，乙酸乙酯在WP中的质量分数较高；在醛类物质中，苯甲醛在BX中的质量分数较高；在酸类物质中，异戊酸在WX中的质量分数最高；在吡嗪类化合物中，四甲基吡嗪在WX中的质量分数最高，表明不同大曲的曲皮、曲心中的挥发性物质质量分数存在一定的差异性。【结论】该研究可为后续研究酱香型高温大曲微生物群落进化和挥发性物质的机制研究提供理论依据。

Abstract:

[Objective] This study aims to explore the physicochemical indicators, microbial diversity, and volatile substances in the Qupi (surface) and Quxin (core) of high-temperature Daqu.[Method] High-throughput sequencing and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were employed to compare the microbial diversity, volatile substances, and physicochemical indicators between Qupi and Quxin of three types of Daqu.[Result] The moisture mass fraction in Qupi of the three types of Daqu was lower than that in Quxin (P<0.05), and the moisture mass fraction was the lowest in the Qupi of white Daqu (WP) and the highest in the Quxin of yellow Daqu (YX). The acidity of Qupi and Quxin were in the order of Quxin of black Daqu (BX) > YX > Qupi of black Daqu (BP) > Quxin of white Daqu (WX) > Qupi of yellow Daqu (YP) > WP. High-throughput sequencing results showed that Firmicutes and Proteobacteria were the dominant bacterial phyla, and Ascomycota was the dominant fungal phylum in Daqu. At the genus level, Pseudomonas_E was the dominant bacterial phyla in BP, BX, and YX; Blastococus was the dominant bacterial phyla in WP; and Scopulibacillus was the dominant bacterial phyla in WX. Thermomyces was the dominant fungal genus in all the samples, while its relative abundance varied among samples. In addition, the microbial diversity in Qupi of Jiangxiangxing high-temperature Daqu was higher than that in Quxin. The redundancy analysis (RDA) results indicated that moisture content and temperature were positively correlated with WP, and YX and BX were positively correlated with acidity. The microbial community structure difference between Qupi and Quxin was mainly attributed to the micro-ecosystem difference. The quantitative analysis results of 76 volatile substances in Qupi and Quxin showed that among esters, the mass fraction of ethyl acetate in WP was relatively high; among aldehydes, the mass fraction of benzaldehyde in BX was relatively high; among acids, isovaleric acid has the highest mass fraction in WX; among pyrazines, tetramethyl pyrazine has the highest mass fraction in WX. The results indicated the mass fractions of volatile substances were different in Qupi and Quxin of different types of Daqu.[Conclusion] This study provides a theoretical foundation for further research on the evolution of microbial communities and the mechanism of volatile substances in Jiangxiangxing high-temperature Daqu.