Fouling analysis and permeate quality evaluation of mulberry wine in microfiltration process.

Sterilization and clarification are essential to produce wine of high quality and stability, microfiltration is a serious candidate for both purposes. In this work, microfiltration of fermented mulberry wine was evaluated for the first time. Four different commercial membranes, of two different materials (PES, PVDF) and two different nominal pore sizes (0.22 µm and 0.45 µm) were employed. Pore blocking model was used to identify the fouling mechanism, foulant constituents were revealed by FT-IR spectra. The effect of microfiltration on permeate quality of mulberry wine was also involved. The results indicated that cake formation was the dominant mechanism during steady-state of mulberry wine microfiltration, independently on the membrane property. The fouling layer was mainly composed of protein and polysaccharides, which induced basically reversible overall filtration resistance. Microfiltration delivered a superior clarity, highly polydisperse and light-color mulberry wine with a satisfactory sterilization stability. It preserved the main basic properties and organic acid contents of mulberry wine while resulted in certain loss of volatile compounds, especially esters and alcohols. This work has provided a scientific reference for producing mulberry wine, a modern functional beverage.

Novel intestinal-targeted Ca-alginate-based carrier for pH-responsive protection and release of lactic acid bacteria.

A novel intestinal-targeted carrier for pH-responsive protection of lactic acid bacteria in stomach and rapid release of lactic acid bacteria in small intestine is successfully developed. The proposed carrier is composed of a Ca-alginate/protamine (CAP) composite shell and a Lactobacillus-casei-encapsulated Ca-alginate (CA) core. The carriers are prepared simply by a coextrusion minifluidic and subsequent adsorption method. The CAP composite shell offers not only improved protection for Lactobacillus casei to guarantee the endurance and survival in the stomach but also satisfactory intestinal-targeted characteristics to guarantee the rapid release of Lactobacillus casei in the small intestine. In the stomach, where there is an acidic environment, the diffusion channels delineated by the CA networks in the CAP composite shell of the carriers are choked with protamine molecules; as a result, it is hard for the gastric acid to diffuse across the CAP composite shell and thus the encapsulated Lactobacillus casei inside carriers can be efficiently protected. However, when they come to the small intestine, where there is a neutral environment, the carriers dissolve rapidly because of the cooperation between protamine and trypsin; consequently, the encapsulated Lactobacillus casei can be quickly released. The proposed CAP composite carrier provides a novel mode for developing efficient protection systems, responsive controlled-release systems, and intestinal-targeted drug delivery systems.

Characterization of eubacterial and archaeal community diversity in the pit mud of Chinese Luzhou-flavor liquor by nested PCR-DGGE.

The aim of this study was to investigate and compare the microbial community structures of eubacteria and archaea in the pit mud of Chinese Luzhou-flavor liquor from the wall (C(w)) and bottom (C(b)) of cellar through nested PCR-denaturing gradient gel electrophoresis (DGGE). The Shannon-Wiener index (H) calculated from the DGGE profiles showed that the community diversities of eubacteria and archaea in samples from C(b) were almost higher than that from C(w). In addition, cluster analysis of the DGGE profiles revealed that some differences were found in the microbial community structure in samples from different locations. The closely relative microorganisms of all eubacterial 16S rRNA gene sequences fell into four phyla (Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria), including 12 genera and 2 uncultured eubacteria. Moreover, 37.1% eubacteria were affiliated with Clostridium. Particularly, genus Acinetobacter was absent in all samples from C(b) but present in all samples from C(w). The closely relative microorganisms of all archaeal 16S rRNA gene sequences fell into four genera, which included Methanobrevibacter, Methanoculleus, Methanobacterium and Methanosaeta, while the dominant archaea in samples from C(w) and C(b) were similar. Results presented in this study provide further understanding of the spatial differences in microbial community structure in the pit mud, and is of great importance for the production and quality improvement of Luzhou-flavor liquor.

[Microbial community structure in strong aromatic liquor fermented grains characterized by PLFA fingerprints].

Taking the nine common microbial strains in liquor-making process as test objects, this paper studied the characteristics of phospholipid fatty acid (PLFA), a characteristic component of the strains cell membrane, and the relationships between the detected amount of PLFA and the biomass of the strains. There existed significant differences in the PLFA fingerprints between test bacteria, actinomycetes, molds, and yeasts, and the PLFA fingerprint of each strain could be used as the basis to distinguish species and genus. Within a certain range of the strains biomass, the detected amount of total PLFA or 16:0 was linearly correlated with the biomass. After adding different biomass Gram positive (G+) bacteria, Gram negative (G-) bacteria, and fungi in fermented grains, a significant difference was observed in the relative amount of PLFA between experimental and control samples. It was suggested that the fingerprint of PLFA could quantitatively or semi-quantitatively characterize the microbial community structure and its dynamic variation in fermented grains. By detecting the PLFA profiles of fermented grains in various liquor industries and by analyzing the microbial community structure in the fermented grains, it was substantiated that PLFA fingerprinting was of general applicability.

[Characteristics of microbial community structure in Luzhou-flavor fermentation pits].

Fermentation pit is a kind of solid bioreactors with unique feature for brewing liquor, especially for Luzhou-flavor, which has significant effects on the quality of produced liquor. There exists a close and complicated correlation between pit age (using time) and microbial community. Taking the characteristic component phospholipid fatty acid (PLFA) in microbial cell membrane as an index, this paper studied the characteristics of the microbial community structure in the pit mud, fermented grains, and yellow water of different age (5-year, 100-year, and 300-year) fermentation pits. The results showed that the total PLFA content was the highest in pit mud, followed by in fermented grains, and in yellow water. The composition of PLFA differed with pit age, and the total PLFA content in yellow water decreased with increasing pit age. In pit mud, straight chain saturated fatty acid had the highest content, occupying 50.7-73.3% of total PLFA and being the highest in 300-year pit. As for the microbial community structure, the PLFA content characterizing Gram-positive (G+) anaerobic bacteria was higher in pit mud, and that characterizing Gram-negative (G-) anaerobic bacteria was higher in fermented grains and yellow water. The PLFA content characterizing G+ and G- bacteria in the pit mud of 100-year pit was higher than that in the pit mud of other ages' pits, while the PLFA content characterizing fungi was higher in the pit mud, fermented grains, and yellow water of 5-year pit, as compared with other ages' pits. Principal component analysis showed that the main varied microbial populations in 5- and 100-year pits were G- bacteria and fungi, and the main varied microbial population in 300-year pit was of bacteria. The indices frequency index, Simpson index, and Shannon index could be chosen for characterizing the diversity of microbial community in fermentation pits.