l-amino acid ligase: A promising alternative for the biosynthesis of l-dipeptides.

Given their special action mechanisms and structural simplicity, L-amino acid ligases (Lals) are considered to be desirable tools for the catalytic biosynthesis of dipeptides. Ywf E (BacD) was the first Lal identified and was shown to be involved in the biosynthesis of a potent antibacterial, bacilysin, since then, various novel Lals have been discovered. Each Lal has different substrate spectra and is capable of synthesizing different dipeptides. Owning to their great potentials for producing bioactive dipeptides of industrial importance, in this review, recent developments of Lals are discussed, including their structures, action mechanisms, applications and the advantages and disadvantages of different Lals. In addition, protein engineering of Lals to improve their substrate specificity and catalytic performance is also discussed.

Effect of xanthan gum on the prevention of intra-abdominal adhesion in rats.

Postoperative adhesions remain a significant concern following abdominal surgery. Polymer barriers are widely used to prevent adhesions, although none have been able to completely prevent adhesions in all situations. Therefore, it is still crucial to develop new products that are effective in a variety of surgical applications. In this study, XG with different concentrations (0.5%-2%, w/v) and molecular weight (Mw) (2.5 × 106 Da-6.9 × 106 Da) were prepared to estimate their potential application as an injectable tissue adhesion barrier. The results showed that XG exerts an anti-adhesion effect in the rat abdominal cavity. For XG with Mw of 5.5 × 106 Da, a 1% or greater concentration was needed to form a gel with required effect as an anti-adhesion agent. The 1% XG gel with high Mw (6.9 × 106 Da) was more effective for the prevention of adhesions compared to a commercially available gel (1.2% sodium hyaluronate). Histological and cytotoxic evaluation demonstrated that XG gel showed no side effect during wound healing, and had no in vitro cytotoxicity to L929 cells. Moreover, rheological analysis was conducted to correlate the anti-adhesion effect with the rheological behavior of XG gels. This investigation suggests that XG has good potential value in intra-abdominal adhesion prevention.

Role of foam drainage in producing protein aggregates in foam fractionation.

It is essential to obtain a clear understanding of the foam-induced protein aggregation to reduce the loss of protein functionality in foam fractionation. The major effort of this work is to explore the roles of foam drainage in protein aggregation in the entire process of foam fractionation with bovine serum albumin (BSA) as a model protein. The results show that enhancing foam drainage increased the desorption of BSA molecules from the gas-liquid interface and the local concentration of desorbed molecules in foam. Therefore, it intensified the aggregation of BSA in foam fractionation. Simultaneously, it also accelerated the flow of BSA aggregates from rising foam into the residual solution along with the drained liquid. Because enhancing foam drainage increased the relative content of BSA molecules adsorbed at the gas-liquid interface, it also intensified the aggregation of BSA during both the defoaming process and the storage of the foamate. Furthermore, enhancing foam drainage more readily resulted in the formation of insoluble BSA aggregates. The results are highly important for a better understanding of foam-induced protein aggregation in foam fractionation.

Oral administration of heparin or heparosan increases the Lactobacillus population in gut microbiota of rats.

Heparin and heparosan have been confirmed to be effective blockers in inhibiting adhesion of pathogens in vitro. However, their effects on gut microbiota in vivo remain unknown. Here we have studied the effects of oral administration of heparin or heparosan on gut microbiota in rats by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Results showed that the predominant bacterial communities in the feces of heparin- or heparosan-treated animals were different from those of the saline-treated animals, with increased Lactobacillus spp. and decreased Enterococcus sp. Different DGGE banding patterns were also observed for the subpopulations of Lactobacillus and Bacteroides groups. In conclusion, heparin or heparosan may be used as an effective gut microbiota modulator by increasing the subpopulation of Lactobacillus.