排序方式: 共有395条查询结果,搜索用时 15 毫秒
391.
392.
Ehsan Mahdinia Ali Demirci Aydin Berenjian 《Bioprocess and biosystems engineering》2017,40(10):1507-1517
Menaquinone-7 (MK-7), a subtype of vitamin K, has received a significant attention due to its effect on improving bone and cardiovascular health. Current fermentation strategies, which involve static fermentation without aeration or agitation, are associated with low productivity and scale-up issues and hardly justify the commercial production needs of this vitamin. Previous studies indicate that static fermentation is associated with pellicle and biofilm formations, which are critical for MK-7 secretion while posing significant operational issues. Therefore, the present study is undertaken to evaluate the possibility of using a biofilm reactor as a new strategy for MK-7 fermentation. Bacillus species, namely, Bacillus subtilis natto, Bacillus licheniformis, and Bacillus amyloliquifaciens as well as plastic composite, supports (PCS) were investigated in terms of MK-7 production and biofilm formation. Results show the possibility of using a biofilm reactor for MK-7 biosynthesis. Bacillus subtilis natto and soybean flour yeast extract PCS in glucose medium were found as the most potent combination for production of MK-7 as high as 35.5 mg/L, which includes both intracellular and extracellular MK-7. 相似文献
393.
394.
395.
Proton exchange between cells and medium is one of the most important factors affecting culture pH, and hence its prediction
is advantageous. In this research, proton exchange flux across the cell membrane was predicted using a genome-scale model.
Calculated proton exchange flux was then exploited as a criterion to predict the trends and intensities of pH changes in cultures
of Bacillus subtilis containing various C-sources, i.e. glucose, sucrose, glycerol, lactate, and citrate, as well as N-sources, i.e. ammonium chloride, sodium nitrate, urea, and histidine. The results showed that glucose, sucrose, and glycerol lowered culture
pH as compared to citrate and lactate, which raised it. With regard to N-sources, the model predicted that ammonium chloride
lowered culture pH while other sources raised pH. Furthermore, maximum theoretical biomass yield using the various C&N-sources
was calculated, and sensitivity of microbial growth to proton exchange flux was investigated using robustness analysis to
identify the effect of pH on growth of B. subtilis using different substrates. Finally, the effect of ammonium nitrate, a widely used nitrogen source, on growth of B. subtilis was studied. Experimental data obtained by cultivation of B. subtilis DSM 3256 on mineral salt media containing various C&N-sources were used to confirm model predictions. Model predictions were
in good agreement with the experimental results for all of the examined C-sources as well as ammonium chloride and sodium
nitrate as N-sources. However, the predictions for the N-sources urea and histidine showed deviations, possibly because these
two compounds serve as both C&N-sources. 相似文献