Bifidobacterium bifidum relieved DSS-induced colitis in mice potentially by activating the aryl hydrocarbon receptor.

Inflammatory bowel disease (IBD) characterized by relapsed intestinal inflammation and barrier function disruption is still a great therapeutic challenge. This study aimed to screen probiotics that have the potential to help alleviate IBD and further elucidate their mechanism of action. Caco-2 cell differentiated monolayers and RAW264.7 cells stimulated by lipopolysaccharide (LPS) were used for probiotic screening in vitro, and then the efficacies of the obtained six bacterial strains were evaluated in mice with dextran sulfate sodium (DSS)-induced colitis. The results showed that all of the strains at varying degrees could increase the transepithelial electrical resistance (TEER) value, decrease the influx of FITC-dextran in Caco-2 cell monolayers and attenuate the production of nitric oxide (NO), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in LPS-stimulated RAW264.7 cells. In vivo experiments indicated that Bifidobacterium bifidum FL-276.1 (FL-276.1) and Bifidobacterium bifidum FL-228.1 (FL-228.1) showed the best efficacies to ameliorate body weight loss, colon shortening, and intestinal barrier disruption. Accordingly, in FL-276.1 and FL-228.1 groups, the genes of zonula occludens-1 (ZO-1), claudin-4, occludin and mucin 2 (Muc2) in mouse colonic tissues were significantly upregulated, while TNF-α, IL-1ß and IL-6 were downregulated. Further results showed that strains FL-276.1 and FL-228.1 could activate the aryl hydrocarbon receptor (AhR) in the intestine. Our study showed that the two Bifidobacterium bifidum strains, FL-276.1 and FL-228.1, ameliorated DSS-induced colitis by enhancing the intestinal barrier and anti-inflammation potentially via the AhR pathway.

Screening, purification, and characterization of an extracellular lipase from Aureobasidium pullulans isolated from stuffed buns steamers.

An extracellular lipase from Aureobasidium pullulans was obtained and purified with a specific activity of 17.7 U/mg of protein using ultrafiltration and a DEAE-Sepharose Fast Flow column. Characterization of the lipase indicated that it is a novel finding from the species A. pullulans. The molecular weight of the lipase was 39.5 kDa, determined by sodium dodecyl sulfonate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited its optimum activity at 40 °C and pH of 7. It also showed a remarkable stability in some organic solutions (30%, v/v) including n-propanol, isopropanol, dimethyl sulfoxide (DMSO), and hexane. The catalytic activity of the lipase was enhanced by Ca2+ and was slightly inhibited by Mn2+ and Zn2+ at a concentration of 10 mmol/L. The lipase was activated by the anionic surfactant SDS and the non-ionic surfactants Tween 20, Tween 80, and Triton X-100, but it was drastically inhibited by the cationic surfactant cetyl trimethyl ammonium bromide (CTAB). Furthermore, the lipase was able to hydrolyze a wide variety of edible oils, such as peanut oil, corn oil, sunflower seed oil, sesame oil, and olive oil. Our study indicated that the lipase we obtained is a potential biocatalyst for industrial use.

Spoilage potential of psychrotrophic bacteria isolated from raw milk and the thermo-stability of their enzymes.

The storage and transportation of raw milk at low temperatures promote the growth of psychrotrophic bacteria and the production of thermo-stable enzymes, which pose great threats to the quality and shelf-life of dairy products. Though many studies have been carried out on the spoilage potential of psychrotrophic bacteria and the thermo-stabilities of the enzymes they produce, further detailed studies are needed to devise an effective strategy to avoid dairy spoilage. The purpose of this study was to explore the spoilage potential of psychrotrophic bacteria from Chinese raw milk samples at both room temperature (28 °C) and refrigerated temperature (7 °C). Species of Yersinia, Pseudomonas, Serratia, and Chryseobacterium showed high proteolytic activity. The highest proteolytic activity was shown by Yersinia intermedia followed by Pseudomonas fluorescens (d). Lipolytic activity was high in isolates of Acinetobacter, and the highest in Acinetobacter guillouiae. Certain isolates showed positive ß-galactosidase and phospholipase activity. Strains belonging to the same species sometimes showed markedly different phenotypic characteristics. Proteases and lipases produced by psychrotrophic bacteria retained activity after heat treatment at 70, 80, or 90 °C, and proteases appeared to be more heat-stable than lipases. For these reasons, thermo-stable spoilage enzymes produced by a high number of psychrotrophic bacterial isolates from raw milk are of major concern to the dairy industry. The results of this study provide valuable data about the spoilage potential of bacterial strains in raw milk and the thermal resistance of the enzymes they produce.

Insights into the microbial diversity and community dynamics of Chinese traditional fermented foods from using high-throughput sequencing approaches.

Chinese traditional fermented foods have a very long history dating back thousands of years and have become an indispensable part of Chinese dietary culture. A plethora of research has been conducted to unravel the composition and dynamics of microbial consortia associated with Chinese traditional fermented foods using culture-dependent as well as culture-independent methods, like different high-throughput sequencing (HTS) techniques. These HTS techniques enable us to understand the relationship between a food product and its microbes to a greater extent than ever before. Considering the importance of Chinese traditional fermented products, the objective of this paper is to review the diversity and dynamics of microbiota in Chinese traditional fermented foods revealed by HTS approaches.

A study revealing the key aroma compounds of steamed bread made by Chinese traditional sourdough.

Aroma of Chinese steamed bread (CSB) is one of the important parameters that determines the overall quality attributes and consumer acceptance. However, the aroma profile of CSB still remains poorly understood, mainly because of relying on only a single method for aroma extraction in previous studies. Therefore, the objective of this study was to determine the volatile aroma compounds of five different samples of CSB using three different aroma extraction methods, namely solid-phase microextraction (SPME), simultaneous distillation-extraction (SDE), and purge and trap (P&T). All samples showed a unique aroma profile, which could be attributed to their unique microbial consortia. (E)-2-Nonenal and (E,E)-2,4-decadienal were the most prevalent aromatic compounds revealed by SDE, which have not been reported previously, while ethanol and acetic acid proved to be the most dominant compounds by both SPME and P&T. Our approach of combining three different aroma extraction methods provided better insights into the aroma profile of CSB, which had remained largely unknown in previous studies.