Biomedical subjects

Xin-Qing Zhao

Publications and source records attributed to Xin-Qing Zhao.

3 recordsLinked to original sources

PubMed2026

Metabolic engineering of Candida yeasts for biotechnological applications.

Candida yeasts represent a versatile yet underexploited platform for industrial biotechnology. These yeasts utilize a remarkably broad range of carbon sources, particularly for hydrophobic carbon sources, coupled with robust growth and diverse biosynthetic capacities, making them promising hosts for sustainable production of chemicals, fuels, and proteins. Despite these advantages, industrial deployment of Candida species has been hindered by concerns regarding opportunistic pathogenicity and the historical lack of efficient genetic manipulation tools, leading to a substantial gap between metabolic potential and practical utilization. Recent advances in functional genomics, genome editing, and systems metabolic engineering are rapidly overcoming these barriers, enabling more precise and efficient strain development. In this review, we systematically summarize recent progress in the metabolic engineering of Candida species as microbial cell factories, with particular emphasis on expanding genetic toolkits, utilizting renewable and non-conventional carbon sources, and biosynthesizing high-value compounds. In addition, we propose a biosafety-oriented classification framework to support their safe industrial deployment. Finally, we discuss current challenges and emerging opportunities, emphasizing that the synergy of synthetic biology and artificial intelligence-driven design holds the key to unlocking the biotechnological potential of Candida yeasts.

Candida↗

PubMed2005

[Continuous ethanol fermentation using self-flocculating yeast strain and bioreactor system composed of multi-stage tanks in series].

A continuous ethanol fermentation system composed of four-stage tank fermentors in series and with a total working volume of 4000 mL was established. The first fermentor was designated as the seed fermentor and the others for ethanol fermentation. A self-flocculating yeast strain developed by protoplast fusion of Saccharomyces cerevisiae and Schizosaccharomyces pombe was applied. Two-stage corn powder enzymatic hydrolyzate containing reducing sugar 100 g/L, together with 2.0 g/L (NH4)2HPO4 and KH2PO4, was used as yeast seed culture medium and fed into the seed fermentor at the dilution rate of 0.017h (-1). Meanwhile, the hydrolyzate containing reducing sugar 220 g/L, added with 1.5 g/L (NH4)2HPO4 and 2.5 g/L KH2PO4, was used as ethanol fermentation substrate and fed into the second fermentor at the dilution rates of 0.017, 0.025, 0.033, 0.040 and 0.050 h(-1) (based on the total working volume of the three fermentors), respectively. The chemostat states on which all of the monitoring parameters, including residual sugar, ethanol and yeast cell biomass concentrations, were maintained relatively constant were observed for seed cultivation and ethanol fermentations when the fermentation system was operated at the dilution rates of 0.017, 0.025, 0.033 and 0.050 h(-1). Yeast cells were observed being partly immobilized because significant yeast cell biomass concentration differences between the broth out of and inside the fermentors were detected. Moreover, the oscillations of residual sugar, ethanol and yeast cell biomass concentrations were observed when the fermentation system was operated at the dilution rate of 0.040 h(-1). The broth containing more than 12% (V/V) ethanol and less than 0.11% (W/V) residual reducing sugar and 0.35% (W/V) residual total sugar was produced when the dilution rate was controlled at no more than 0.033 h(-1). The ethanol productivity was calculated to be 3.32(g x L(-1) x h(-1)) for the dilution rate of 0.033 h(-1), which increased nearly 100% compared with that for conventional ethanol fermentation technologies using freely suspended yeast cells.

Bioreactors↗

PubMed2004

Widespread activation of antibiotic biosynthesis by S-adenosylmethionine in streptomycetes.

The effect of S-adenosylmethionine (SAM) on the production of various antibiotics was investigated to determine whether SAM-dependent methylation is required in biosynthetic pathways of antibiotics. Pristinamycin II(B) and granaticin do not require SAM-dependent methylation in their biosynthesis pathways, and production of these two antibiotics was increased about 2-fold when a low concentration (50 and 10 microM, respectively) of SAM was treated; in contrast, oleandomycin and avermectin B1a require SAM as a methyl donor in their biosynthesis, and production of these two antibiotics was increased 5-fold and 6-fold, depending on the SAM concentration within a certain range. We also found that the transcription of a pathway-specific regulator, gra-ORF9, was activated by exogenous SAM treatment. Production of oleandomycin and avermectin B1a was decreased by using a methyltransferase inhibitor, sinefungin, but the production levels of these antibiotics were restored to the control level by simultaneously adding SAM and sinefungin. Interestingly, we have found a similar stimulatory effect of S-adenosylhomocysteine (SAH), the methylation product of SAM, on antibiotic production in the four strains. Our results clearly demonstrate the widespread activation of antibiotic production using SAM in streptomycetes.

Anti-Bacterial Agents↗