Guohong Gong

Isolation and characterization of lipopeptide antibiotics produced by Bacillus subtilis

Aims:  Antibiotics from Bacillus subtilis JA show strong pathogen inhibition ability, which has potential market application; yet, the composition of these antibiotics has not been elucidated. The aim of this paper is to isolate and identify these antibiotics.

Improving Aspergillus niger tannase yield by N+ ion beam implantation

This work aimed to improve tannase yield of Aspergillus niger through N+ ion beam implantation in submerged fermentation. The energy and dose of N+ ion beam implantation were investigated. The results indicated that an excellent mutant was obtained through nine successive implantations under the conditions of 10 keV and 30-40 (×2.6×1013) ions/cm2, and its tannase yield reached 38.5 U/mL, which was about five-time higher than the original strain. The study on the genetic stability of the mutant showed that its promising performance in tannase production could be stable. The studies of metal ions and surfactants affecting tannase yield indicated that manganese ions, stannum ions, xylene and SDS contained in the culture medium had positive effects on tannase production under submerged fermentation. Magnesium ions, in particular, could enhance the tannase yield by the mutant increasing by 42%, i.e. 53.6 U/mL. Accordingly, low-energy ion implantation could be a desirable approach to improve the fungal tannase yield for its commercial application.

Metabolic engineering of Penicillium chrysogenum morphology

Filamentous fungi are widely used in the field of industrial fermentation, and their morphological diversity and complex regulation during fermentation have attracted serious attention from researchers. Penicillium chrysogenum morphology, intervention and regulation, as well as the relationship between morphology and yield, were researched in this study. We have established an effective image processing method to measure several hyphal morphological parameters. These parameters were applied to quantitative analysis of morphology and the metabolic status of the product under different culture conditions. Simultaneously, morphological dynamics equations were also established. Low energy ion beam implantation and low temperature air plasma techniques were used in this work to mutate P. chrysogenum . To reveal the relationship between hyphal morphology and the production of secondary metabolites, quantitative analysis of hyphal morphological variations in the fermentation process was also carried out with mutant strains and the original strain. We constructed an RNAi vector to silence the class III chitin synthase gene chs4 to construct morphological mutants. All transformants except PcRNAi1-15 exhibited enhanced penicillin yields, especially PcRNAi1-17 and PcRNAi2-1, whose yields were 27% and 41% higher than the original strain. Our results provide a theoretical basis for understanding the regulatory mechanisms of penicillin production.