A DGGE Marker-Mediated Fast Monitoring of Bacterial Diversity and Comprehensive Identification of High-Temperature Daqu Starter.

Abstract

Bacteria play an essential role in Daqu starter (Daqu) fermentation. The identification of Daqu bacteria was investigated by polymerase chain reaction (PCR) based denaturing gradient gel electrophoresis (DGGE) analysis of the highly variable V3 region of the 16S rRNA gene. Here, we define a novel DGGE marker for the quick identification of Daqu bacteria. A dynamic alteration of the bacterial populations at different stages of fermentation was determined through a 2-y continuous monitoring. The physicochemical parameters of Daqu at different fermentation stages were investigated by weighing, NaOH titration, and HCl hydrolysis together with Fehling reagent methods. Furthermore, infrared spectral analysis using Fourier Transformed Infrared Spectroscopy was performed to determine physicochemical changes of Daqu. Therefore, our studies provide key insight for a comprehensive quality control of Daqu at different fermentation stages using the PCR-DGGE analysis combined with the physicochemical measurement. Chinese liquor is one of the 6 well-known distilled spirits in the world. High-temperature Daqu acts as an important source of nutrients and of microorganisms in the solid-state fermentation of Chinese Moutai-flavor liquor, which has a critical impact on the final flavor of the liquor. The study identifies a novel DGGE marker and provides an efficient way to identify bacterial diversity in Daqu from different fermentation stages. Importantly, the study defines dynamic changes of the physicochemical parameters and the infrared spectra analysis of Daqu during the fermentation process. These studies will help to (1) establish a standard operation procedure for Daqu production; (2) stabilize manufacturing process for Daqu fermentation and even for liquor brewing.