Xuxia Zhou

Differences in amino acids composition and coupling patterns between mesophilic and thermophilic proteins

Summary.Thermophilic proteins show substantially higher intrinsic thermal stability than their mesophilic counterparts. Amino acid composition is believed to alter the intrinsic stability of proteins. Several investigations and mutagenesis experiment have been carried out to understand the amino acid composition for the thermostability of proteins. This review presents some generalized features of amino acid composition found in thermophilic proteins, including an increase in residue hydrophobicity, a decrease in uncharged polar residues, an increase in charged residues, an increase in aromatic residues, certain amino acid coupling patterns and amino acid preferences for thermophilic proteins. The differences of amino acids composition between thermophilic and mesophilic proteins are related to some properties of amino acids. These features provide guidelines for engineering mesophilic protein to thermophilic protein.

Effect of dietary probiotic, Bacillus coagulans, on growth performance, chemical composition, and meat quality of Guangxi Yellow chicken

The effect of Bacillus coagulans ZJU0616 with different concentrations supplemented as probiotic was evaluated on growth performance, feed conversion ratio, survival rate, breast chemical composition, and meat quality of Guangxi Yellow chicken. Birds were randomly segregated into 12 groups so that 3 replicates were available for each of the 3 treatments (T-1, T-2, and T-3) and control groups. The control groups were fed a basal diet without any probiotic and other groups were fed the diets that consisted of 3 probiotic levels at initial concentrations of 1.0 x 10(6) cfu.g(-1) (T-1), 2.0 x 10(6) cfu.g(-1) (T-2), and 5.0 x 10(6) cfu.g(-1) (T-3). The lowest final weight and daily weight gain were found in control groups (P < 0.05) and there were no significant differences among probiotic-treated groups. Significantly lower feed conversion ratio and higher survival rate were observed in T-2 and T-3 than that of the control. There were no significant differences (P > 0.05) in contents of breast chemical composition including moisture, CP, crude fat, and crude ash among all groups. For the meat quality parameter assays, the pH, shear force, and drip loss were used as indicators. As for pH values of breasts, no significant difference was found across all treatments. Higher shear force was observed (P < 0.05) in T-2 compared with T-1 and the control. Similar significant difference was also observed in T-1 compared with the control. However, there was no significant difference in shear force between T-3 and the other probiotic treatment groups (T-1 and T-2). As for probiotic-treated groups, there was significant difference (P < 0.05) in breast drip loss compared with that of the control (6.22 +/- 0.18%), with the lowest drip loss found in T-3 (5.38 +/- 0.25%). However, no significant difference was observed in drip loss between T-2 and T-3.

In vitro assessment of gastrointestinal viability of two photosynthetic bacteria, Rhodopseudomonas palustris and Rhodobacter sphaeroides.

The objectives of this study were to assess the potential of two photosynthetic bacteria (PSB), Rhodopseudomonas palustris HZ0301 and Rhodobacter sphaeroides HZ0302, as probiotics in aquaculture. The viability of HZ0301 and HZ0302 in simulated gastric transit conditions (pH 2.0, pH 3.0 and pH 4.0 gastric juices) and in simulated small intestinal transit conditions (pH 8.0, with or without 0.3% bile salts) was tested. The effects of HZ0301 and HZ0302 on the viability and permeability of intestinal epithelial cell in primary culture of tilapias, Oreochromis nilotica, were also detected. All the treatments were determined with three replicates. The simulated gastric transit tolerance of HZ0301 and HZ0302 strains was pH-dependent and correspondingly showed lower viability at pH 2.0 after 180 min compared with pH 3.0 and pH 4.0. Both HZ0301 and HZ0302 were tolerant to simulated small intestine transit with or without bile salts in our research. Moreover, there was no significant difference (P>0.05) among three treatments including the control and the groups treated with HZ0301 or HZ0302 both in intestinal epithelial cell viability and membrane permeability, showing no cell damage. In summary, this study demonstrated that HZ0301 and HZ0302 had high capacity of upper gastrointestinal transit tolerance and were relatively safe for intestinal epithelial cells of tilapias.