Establishing a mucosal gut microbial community in vitro using an artificial simulator.

The Twin Simulator of the Human Intestinal Microbial Ecosystem (TWINSHIME®) was initially developed to study the luminal gut microbiota of the ascending (AC), transverse (TC), and descending (DC) colon regions. Given the unique composition and potential importance of the mucosal microbiota for human health, the TWINSHIME was recently adapted to simulate the mucosal microbiota as well as the luminal community. It has been previously demonstrated that the luminal community in the TWINSHIME reaches a steady state within two weeks post inoculation, and is able to differentiate into region specific communities. However, less is known regarding the mucosal community structure and dynamics. During the current study, the luminal and mucosal communities in each region of the TWINSHIME were evaluated over the course of six weeks. Based on 16S rRNA gene sequencing and short chain fatty acid analysis, it was determined that both the luminal and mucosal communities reached stability 10-20 days after inoculation, and remained stable until the end of the experiment. Bioinformatics analysis revealed the formation of unique community structures between the mucosal and luminal phases in all three colon regions, yet these communities were similar to the inoculum. Specific colonizers of the mucus mainly belonged to the Firmicutes phylum and included Lachnospiraceae (AC/TC/DC), Ruminococcaceae and Eubacteriaceae (AC), Lactobacillaceae (AC/TC), Clostridiaceae and Erysipelotrichaceae (TC/DC). In contrast, Bacteroidaceae were enriched in the gut lumen of all three colon regions. The unique profile of short chain fatty acid (SCFA) production further demonstrated system stability, but also proved to be an area of marked differences between the in vitro system and in vivo reports. Results of this study demonstrate that it is possible to replicate the community structure and composition of the gut microbiota in vitro. Through implementation of this system, the human gut microbiota can be studied in a dynamic and continuous fashion.

Physical and chemical changes in whey protein concentrate stored at elevated temperature and humidity.

In a case study, we monitored the physical properties of 2 batches of whey protein concentrate (WPC) under adverse storage conditions to provide information on shelf life in hot, humid areas. Whey protein concentrates with 34.9 g of protein/100g (WPC34) and 76.8 g of protein/100g (WPC80) were stored for up to 18 mo under ambient conditions and at elevated temperature and relative humidity. The samples became yellower with storage; those stored at 35 °C were removed from the study by 12 mo because of their unsatisfactory appearance. Decreases in lysine and increases in water activity, volatile compound formation, and powder caking values were observed in many specimens. Levels of aerobic mesophilic bacteria, coliforms, yeast, and mold were <3.85 log10 cfu/g in all samples. Relative humidity was not a factor in most samples. When stored in sealed bags, these samples of WPC34 and WPC80 had a shelf life of 9 mo at 35 °C but at least 18 mo at lower temperatures, which should extend the market for these products.

Electrospun Polymer Nanofibers Reinforced by Tannic Acid/Fe+++ Complexes.

We report the successful preparation of reinforced electrospun nanofibers and fibrous mats of polyvinyl alcohol (PVA) via a simple and inexpensive method using stable tannic acid (TA) and ferric ion (Fe+++) assemblies formed by solution mixing and pH adjustment. Changes in solution pH change the number of TA galloyl groups attached to the Fe+++ from one (pH < 2) to two (3 < pH < 6) to three (pH < 7.4) and affect the interactions between PVA and TA. At pH ~ 5.5, the morphology and fiber diameter size (FDS) examined by SEM are determinant for the mechanical properties of the fibrous mats and depend on the PVA content. At an optimal 8 wt % concentration, PVA becomes fully entangled and forms uniform nanofibers with smaller FDS (p < 0.05) and improved mechanical properties when compared to mats of PVA alone and of PVA with TA (p < 0.05). Changes in solution pH lead to beads formation, more irregular FDS and poorer mechanical properties (p < 0.05). The Fe+++ inclusion does not alter the oxidation activity of TA (p > 0.05) suggesting the potential of TA-Fe+++ assemblies to reinforce polymer nanofibers with high functionality for use in diverse applications including food, biomedical and pharmaceutical.