Wenxue Zhang

Analysis of the bacterial community in aged and aging pit mud of Chinese Luzhou‐flavour liquor by combined PCR‐DGGE and quantitative PCR assay

BACKGROUND The community structure of bacteria in aged and aging pit mud, which was judged according to their sensory and physicochemical characteristics, was analysed using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative real-time PCR (qPCR). RESULTS The phyla Firmicutes, Actinobacteria, Proteobacteria, Synergistetes and Unclassified Bacteria were detected and the fermentative Firmicutes was predominant in both types of pit mud in the PCR-DGGE analysis. Among Firmicutes, Clostridiales was dominant in aged pit mud while Bacillales and Lactobacillales were dominant in aging pit mud. The diversity of bacterial communities in aged pit mud was higher than that in aging pit mud. In the qPCR analysis the abundance of Clostridium IV in aged pit mud was higher than that in aging pit mud and there were significant differences in the quantity of Clostridium IV between aged and aging pit mud of the same cellar (P < 0.05). CONCLUSION There were some significant differences in the microbial community structure between aged and aging pit mud. The differences in the quantity of Clostridium IV might be involved in the distinction that the aged pit mud has a strong aroma while the aging pit mud does not.

Phylogenetic Diversity Analysis of Archaeal in the Pit Mud with Different Cellar Age

In order to investigate the clusters and succession rules of archaeal in the pit mud,the total DNAs were extracted from the pit mud with cellar age of 20,50 and 150 years,respectively.The community structure was studied by polymerase chain reaction-amplified rDNA restriction analysis(PCR-ARDRA) and sequencing of 16S rDNA.The results showed that 191 clones from the 16S rDNA library fell into 22 operational taxonomic units(OTUs) from 6 groups including Methanosarcina,Methanobacterium,Methanoculleus,Methanocorpusculum,Methanosaeta and Methanospirillum.Diversity was obvious in the predominant archaeal from the pit mud with different cellar age.The predominant archaeal from the pit mud with cellar age of 20 years were Methanosarcina and Methanosaeta,which produced methane by utilizing acetic acid.However,the predominant archaeal from the pit mud with cellar age of 50 and 150 years were Methanocorpusculum and Methanobacterium,which utilizing hydrogen.With the increasing cellar age,the Shannon-Wiener index(H) and Berger-Parker index(D) of archaeal in the pit mud showed an increasing trend,while the Pielou index(J) showed a decreasing trend.The Sorenson similarity index of the pit mud with different cellar age was the range of 0.429~0.677,and there was the highest similarity of community structure between the pit mud with cellar age of 50 and 150 years.This study revealed the relationship between archaeal phylogenetic diversity of pit mud and the aging of pit mud.

Anaerobic detoxification fermentation by Rhodospirillum rubrum for rice straw as feed with moderate pretreatment

ABSTRACT A novel and effective process was put forward for converting rice straw into feed by combining diluted acid hydrolysis and ammonization with Rhodospirillum rubrum fermentation. After pretreatment with dilute sulfuric or phosphoric acid (1%, w/w) at 100°C, materials were subjected to fermentation under several gases (N2, CO2, and air) and different light intensities in a 2-L fermentor. The key indexes of feed for fermented materials were estimated and several toxic substances were investigated during the fermentation. Following sulfuric acid treatment, the true protein of rice straw increased from 29 to 143 g kg−1 and the crude fiber decreased from 359 to 136 g kg−1 after fermentation at 0.3 L min−1 L−1 of N2 flow and a light intensity of 3400 lux; and following phosphoric acid treatment, the true protein increased by 286% and the crude fiber decreased by 52% after fermentation at 0.4 L min−1 L−1 of N2 flow and a light intensity of 3000 lux. Other key contents were also improved for use as feed, and some toxic substances (i.e., furfural, hydroxymethylfurfural, acetic acid, phenol, cresol) produced by the pretreatments could be removed at low levels during the fermentations.

Dynamic and Functional Characteristics of Predominant Species in Industrial Paocai as Revealed by Combined DGGE and Metagenomic Sequencing

The microbial community during the fermentation of industrial paocai, a lactic acid fermented vegetable food, was investigated via combined denaturing gradient gel electrophoresis (DGGE) and metagenomic sequencing. Firmicutes and Proteobacteria were identified as the dominant phyla during the fermentation. DGGE results of the bacterial community analysis showed that many genera were observed during the fermentation of industrial paocai, but the same predominant genus and species were observed: Lactobacillus and Lactobacillus (L.) alimentarius/L. paralimentarius. The abundance of L. alimentarius/L. paralimentarius increased fast during the initial stage of fermentation and approximately remained constant during the later stage. Metagenomic sequencing was used to finally identify the predominant species and their genetic functions. Metabolism was the primary functions of the microbial community in industrial paocai fermentation, including carbohydrate metabolism (CM), overview (OV), amino acid metabolism (AAM), nucleotide metabolism (NM), energy metabolism (EM), etc. The predominant species L. alimentarius and L. paralimentarius were involved in plenty of pathways in metabolism and played different roles in the metabolism of carbohydrate, amino acid, lipid to form flavor compounds during industrial paocai fermentation. This study provided valuable information about the predominant species in industrial paocai and its functional properties, which could enable us to advance our understanding of the fermentation mechanism during fermentation of industrial paocai. Our results will advance the understanding of the microbial roles in the industrial paocai fermentation and provide a theoretical basis for improving the quality of industrial paocai products.