Genhai Zhao

Enhanced Production of Vitamin K2 from Bacillus subtilis (natto)by Mutation and Optimization of the Fermentation Medium

The aim of this study was to enhance the production of vitamin K2 by using N-methyl-N-nitro-N-nitroso-guanidine (NTG) and low energy ion beam implantation and optimizing the fermentation medium. Mutation resulted in 1.66-fold higher production of vitamin K2 than that of the parentl strain. The production by the mutant BN-P15-11-1was increased 55% and reached 3.593±0.107 mg/L by using the Plackett-Burman and Box-Behnken designs to optimize the fermentation medium. The optimal fermentation culture medium was composed of (g/L) glycerol 69.6, sucrose 34.5, K2HPO4 4.0, peptone 20, yeast extract 25 and fermented at 37 °C and 150 rpm for 72 h. The results showed that the NTG and low energy ion beam implantation mutations and optimizing fermentation medium were effective methods to enhance vitamin K2production.

Optimization Medium Composition for Vitamin K2 by Flavobacterium sp. using Response Surface Methodology and Addition of Arachis hypogaea

The purpose of this research was to enhance the production of vitamin K2 by fermentation optimization and Arachis hypogaea supplementation in Flavobacterium sp. mutant SP-L-01. Optimized culture condition were as follows: 6-days shake-flask culture at 37oC with initial pH value 7.0 ± 0.2, shaking speed in 120 r/min and medium volume of 30 mL with 2% inoculums. After optimization of fermentation medium by response surface methodology (RSM), optimized medium were maltose 23.8 g/l, glucose 9.69 g/l, beef extract 15 g/l, K2HPO4 4.5 g/l，NaCl 3.0 g/l and MgSO4·7H2O 0.3 g/l. Production of vitamin K2 after optimization reached to 10.97 mg/l, which is 79.25% higher than that before optimization (6.12 mg/l). 3 mg/mL of arachis hypogaea was added into the medium at 72 h of shake-flake cultivation, which improved the production of menaquinone-4 (MK4) up to 371% and menaquinone-6 (MK6) up to 149% higher than those of the original medium. D-(+)-catechin, one of the components of arachis hypogaea, was added alone into the medium, which also improved the vitamin K2 synthesis.

Macro-morphological characterization and kinetics of Mortierella alpina colonies during batch cultivation

An effective method for research of macro-morphological characterization and its kinetics was developed by studying the macro-morphological characteristics of Mortierella alpina, an oleaginous zygomycete widely used to produce lipids rich in PUFA, in function of culture medium composition and to link morphological features of fungus with the level of lipid production. A number of distinct morphological forms including hollow pellets, fluffy pellets and freely dispersed mycelia were obtained by changing the fermentation factors. By fitting a Logistic curve, the maximum specific growth rate (μmax)was obtained, which determined the final mycelia morphology. μmax of 0.6584 in three kind of morphological forms is the more appropriate. According to the Luedeking-Piret equation fitting, α≠0 and β≠0, lipid production was partially associated with the hyphal growth, fluffy pellets which turn glucose into lipidwas more effective than the other two kinds of morphological forms.

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.