Determination of six groups of mycotoxins in Chinese dark tea and the associated risk assessment.

Chinese dark tea is widely enjoyed for its multiple health-promoting effects and pleasant taste. However, its production involves fermentation by microbiota in raw tea, some of which are filamentous fungi and thus potential mycotoxin producers. Accordingly, whether mycotoxins pose health risk on dark tea consumption has become a public concern.

The Core Role of and in Pile-Fermentation Processing of Qingzhuan Brick Tea.

To identify the microorganisms responsible for the formation of the main quality components of Qingzhuan brick tea (QZBT) during solid-state fermentation (SSF), predominant thermoduric strains were isolated from the tea leaves collected during SSF. According to their capability of releasing cellulase, pectase, protease, and polyphenol oxidase, four strains were selected as starter cultures to ferment sun-dried tea leaves during artificially inoculated SSF. According to the major enzymatic activities and quality components content (tea polyphenols, catechins, amino acids, soluble sugar, and theabrownin), it was found that M1 had a significant effect on the transformation of polyphenols and X4 could enhance the ability of bioconversion of strain M1.

Loading of anthocyanins on chitosan nanoparticles influences anthocyanin degradation in gastrointestinal fluids and stability in a beverage.

The optimal preparation parameters to create anthocyanin-loaded chitosan nanoparticles was predicted using response surface methodology (RSM). A Box-Behnken design was used to determine the preparation parameters that would achieve the preferred particle size and high encapsulation efficiency. The result suggested that the optimized conditions were 2.

Improvement of the respiration efficiency of Lactococcus lactis by decreasing the culture pH.

Objective: The growth characteristics and intracellular hemin concentrations of Lactococcus lactis grown under different culture pH and aeration conditions were examined to investigate the effect of culture pH on the respiration efficiency of L. lactis NZ9000 (pZN8148).

Results: Cell biomass and biomass yield of L.

Exogenous transglutaminase improves multiple-stress tolerance in Lactococcus lactis and other lactic acid bacteria with glutamine and lysine in the cell wall.

Objective: To increase the resistance of ingested bacteria to multiple environmental stresses, the role of transglutaminase in Lactococcus lactis and possible mechanisms of action were explored.

Results: L. lactis grown with transglutaminase exhibited significantly higher resistance to bile salts, stimulated gastric juice, antibiotics, NaCl, and cold stress compared to the control (cultured without transglutaminase), with no negative influence on cell growth.

[Improving industrial microbial stress resistance by metabolic engineering: a review].

Metabolic engineering is a technologic platform for industrial strain improvement and aims not only at modifying microbial metabolic fluxes, but also improving the physiological performance of industrial microbes. Microbes will meet multiple stresses in industrial processes. Consequently, elicited gene responses might result in a decrease in overall cell fitness and the efficiency of biotransformation.

Optimization of a GC-MS metabolic fingerprint method and its application in characterizing engineered bacterial metabolic shift.

Metabolomics influences many aspects of life sciences including microbiology. Here, we describe the systematic optimization of metabolic quenching and a sample derivatization method for GC-MS metabolic fingerprint analysis. Methanol, ethanol, acetone, and acetonitrile were selected to evaluate their metabolic quenching ability, and acetonitrile was regarded as the most efficient agent.

[The function of glutathione/glutathione peroxidase system in the oxidative stress resistance systems of microbial cells].

The physiological roles of the glutathione(GSH)/glutathione peroxidase(GPx) system in protecting microbial cells against oxidative stress were reviewed. In eukaryotic model microbe Saccharomyces cerevisiae,this system is obligatory in maintaining the redox balance and defending the oxidative stress. However, the GSH/GPx system only conditionally exists in prokaryotes.

Glutathione protects Lactococcus lactis against acid stress.

Previously we showed that glutathione (GSH) can protect Lactococcus lactis against oxidative stress (Y. Li et al., Appl.

Introducing glutathione biosynthetic capability into Lactococcus lactis subsp. cremoris NZ9000 improves the oxidative-stress resistance of the host.

This study describes how a metabolic engineering approach can be used to improve bacterial stress resistance. Some Lactococcus lactis strains are capable of taking up glutathione, and the imported glutathione protects this organism against H(2)O(2)-induced oxidative stress. L.

[Glutathione plays an anti-oxidant role in Lactococcus lactis].

To assess the physiological function of GSH in resistance to oxidative stress in Lactococcus lactis ssp. cremoris NZ9000, the recombinant strain NZ9000 (pNZ3203) capable of producing GSH was used as the experiment materials. The anti-oxidant role of glutathione was observed under higher H2O2 dosage, i.

Heterologous leaky production of transglutaminase in Lactococcus lactis significantly enhances the growth performance of the host.

This study describes a novel strategy to improve the growth performance of Lactococcus lactis by heterologous production of food-grade transglutaminase. The mtg gene from Streptoverticillium mobaraense that encodes the transglutaminase mature protein was cloned into a nisin-inducible expression vector and transformed into L. lactis subsp.

[Influence of expression of transglutaminase on the growth of Lactococcus lactis].

To improve the aerobic growth performance of Lactococcus lactis subsp. cremoris NZ9000, the gene mtg encoding the mature microbial transglutaminase was amplified from the chromosomal DNA of Streptoverticillium mobaraense and then cloned into the nisin-inducible expression vector pNZ8148. The resulting plasmid pFL001 was transformed into strain NZ9000 by electroporation.