Hongtao Zhang

Bio: Hongtao Zhang is an academic researcher from Jiangnan University. The author has contributed to research in topics: Fermentation & Fermentation in winemaking. The author has an hindex of 7, co-authored 28 publications receiving 244 citations.

Recent advances in curdlan biosynthesis, biotechnological production, and applications

Abstract: Curdlan is a water-insoluble β-(1,3)-glucan produced by Agrobacterium species under nitrogen-limited condition. Its heat-induced gelling properties render curdlan to be very useful in the food industry initially. Recent advances in the understanding of the role curdlan plays in both innate and adaptive immunity lead to its growing applications in biomedicine. Our review focuses on the recent advances on curdlan biosynthesis and the improvements of curdlan fermentation production both from our laboratory and many others as well as the latest advances on the new applications of curdlan and its derivatives particularly in their immunological functions in biomedicine.

Improved curdlan fermentation process based on optimization of dissolved oxygen combined with pH control and metabolic characterization of Agrobacterium sp. ATCC 31749

Abstract: A significant problem in scale-down cultures, rarely studied for metabolic characterization and curdlan-producing Agrobacterium sp. ATCC 31749, is the presence of dissolved oxygen (DO) gradients combined with pH control. Constant DO, between 5% and 75%, was maintained during batch fermentations by manipulating the agitation with PID system. Fermentation, metabolic and kinetic characterization studies were conducted in a scale-down system. The curdlan yield, intracellular nucleotide levels and glucose conversion efficiency into curdlan were significantly affected by DO concentrations. The optimum DO concentrations for curdlan production were 45–60%. The average curdlan yield, curdlan productivity and glucose conversion efficiency into curdlan were enhanced by 80%, 66% and 32%, respectively, compared to that at 15% DO. No apparent difference in the gel strength of the resulting curdlan was detected. The comparison of curdlan biosynthesis and cellular nucleotide levels showed that curdlan production had positive relationship with intracellular levels of UTP, ADP, AMP, NAD+, NADH and UDP-glucose. The curdlan productivity under 45% DO and 60% DO was different during 20–50 h. However, after 60 h curdlan productivity of both conditions was similar. On that basis, a simple and reproducible two-stage DO control process for curdlan production was developed. Curdlan production yield reached 42.8 g/l, an increase of 30% compared to that of the single agitation speed control process.

Effect of Temperature on Chinese Rice Wine Brewing with High Concentration Presteamed Whole Sticky Rice

Abstract: Production of high quality Chinese rice wine largely depends on fermentation temperature. However, there is no report on the ethanol, sugars, and acids kinetics in the fermentation mash of Chinese rice wine treated at various temperatures. The effects of fermentation temperatures on Chinese rice wine quality were investigated. The compositions and concentrations of ethanol, sugars, glycerol, and organic acids in the mash of Chinese rice wine samples were determined by HPLC method. The highest ethanol concentration and the highest glycerol concentration both were attained at the fermentation mash treated at 23°C. The highest peak value of maltose (90 g/L) was obtained at 18°C. Lactic acid and acetic acid both achieved maximum values at 33°C. The experimental results indicated that temperature contributed significantly to the ethanol production, acid flavor contents, and sugar contents in the fermentation broth of the Chinese rice wines.

Sequence and transcriptional analysis of the genes responsible for curdlan biosynthesis in Agrobacterium sp. ATCC 31749 under simulated dissolved oxygen gradients conditions

Abstract: Expression at the mRNA level of ten selected genes in Agrobacterium sp. ATCC 31749 under various dissolved oxygen (DO) levels during curdlan fermentation related to electron transfer chain (ETC), tricarboxylic acid (TCA) cycle, peptidoglycan/lipopolysaccharide biosynthesis, and uridine diphosphate (UDP)-glucose biosynthesis were determined by qRT-PCR. Experiments were performed at DO levels of 30%, 50%, and 75%, as well as under low-oxygen conditions. The effect of high cell density on transcriptional response of the above genes under low oxygen was also studied. Besides cytochrome d (cyd A), the transcription levels of all the other genes were increased at higher DO and reached maximum at 50% DO. Under 75% DO, the transcriptional levels of all the genes were repressed. In addition, transcription levels of icd, sdh, cyo A, and fix N genes did not exhibit significant fluctuation with high cell density culture under low oxygen. These results suggested a mechanism for DO regulation of curdlan synthesis through regulation of transcriptional levels of ETCs, TCA, and UDP-glucose synthesis genes during curdlan fermentation. To our knowledge, this is the first report that DO concentration apparently regulates curdlan biosynthesis in Agrobacterium sp. ATCC 31749 providing essential lead for the optimization of the fermentation at the industrial scale.

In vitro assessment of prebiotic properties of oligosaccharides derived from four microbial polysaccharides

Abstract: Xanthan gum oligosaccharides (XGOS), gellan gum oligosaccharides (GGOS), pullulan oligosaccharides (POS) and curdlan oligosaccharides (COS) were in a degree of polymerization (DP) of 2–15. The in vitro prebiotic properties of these oligosaccharides were investigated by cultivating Lactobacillus sp., Bifidobacterium sp. and human fecal bacteria. POS and COS were selectively utilized by Lactobacillus and Bifidobacterium strains, resulting in enhanced bacterial growth and lactic and acetic acid production. When these oligosaccharides were used for cultivating healthy human fecal bacteria, POS and COS prefer to enrich Bifidobacterium and Bacteroides, respectively, accompanied by increased SCFAs level. XGOS significantly increased Bacteroides and butyric acid-producing bacteria proliferation and the butyric acid production over a 12–24 h fermentation. GGOS showed similar effects as XGOS due to their shared β (1 → 4) glycosidic bonds. These results demonstrated that COS, POS, XGOS and GGOS are potential as prebiotics. XGOS exerted the best prebiotic effects in enriching the beneficial Bacteroides and butyric acid-producing bacteria proliferation and increasing the SCFAs level.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。