1.
Acidithiobacillus thiooxidans and its potential application.
Yang, L, Zhao, D, Yang, J, Wang, W, Chen, P, Zhang, S, Yan, L
Applied microbiology and biotechnology. 2019;(19):7819-7833
Abstract
Acidithiobacillus thiooxidans (A. thiooxidans) is a widespread, mesophilic, obligately aerobic, extremely acidophilic, rod-shaped, and chemolithoautotrophic gram-negative gammaproteobacterium. It can obtain energy and electrons from the oxidation of reducible sulfur, and it can fix carbon dioxide and assimilate nitrate, nitrite, and ammonium to satisfy carbon and nitrogen requirement. This bacterium exists as different genomovars and its genome size range from 3.02 to 3.97 Mb. Here, we highlight the recent advances in the understanding of the general biological features of A. thiooxidans, as well as the genetic diversity and the sulfur oxidation pathway system. Additionally, the potential applications of A. thiooxidans were summarized including the recycling of metals from metal-bearing ores, electric wastes, and sludge, the improvement of alkali-salinity soils, and the removal of sulfur from sulfur-containing solids and gases.
2.
Progress in the research of S-adenosyl-L-methionine production.
Chu, J, Qian, J, Zhuang, Y, Zhang, S, Li, Y
Applied microbiology and biotechnology. 2013;(1):41-9
Abstract
This minireview mainly aims at the study of S-adenosyl-L-methionine (SAM) production by microbial fermentation. A brief introduction of the biological role and application of SAM was presented. In general, SAM production can be improved by breeding of the producing strain through the conventional mutation or genetic engineering approach in the molecular or cellular scale, by optimization of culture conditions in the cellular scale or bioreactor engineering scale, or by multiscale approach. The productivity of SAM fermentation has been improved greatly through the efforts of many researchers using the methods previously mentioned. The SAM-producing strains used extensively are Pichia pastoris and Saccharomyces cerevisiae. The effect of SAM on antibiotic production was also exemplified. The skill and scheme beneficial to the improvement of SAM production involves the enhancement of SAM synthetase (methionine adenosyltransferase) activity and selection of engineered constitutive promoters with appropriate strength; seeking for and eliminating the rate-limiting factors in SAM synthesis, namely, knocking off the genes that transform SAM and L-methionine (L-Met) to cysteine; release the feedback inhibition of SAM to methylenetetrahydrofolate reductase; blocking the transsulfuration pathway by interfering the responsible enzymes; enhancing ATP level through pulsed feeding of glycerol; and optimizing the L-Met feeding strategy. Precise control of gene expression and quantitative assessment of physiological parameters in engineered P. pastoris were highlighted. Finally, a discussion of the prospect of SAM production was presented.
3.
Improvement of lactic acid production from cellulose with the addition of Zn/Ni/C under alkaline hydrothermal conditions.
Zhang, S, Jin, F, Hu, J, Huo, Z
Bioresource technology. 2011;(2):1998-2003
Abstract
The effect of Zn, Ni and activated carbon on the yield of lactic acid from cellulose was investigated to improve the lactic acid yield under alkaline hydrothermal conditions. The results showed that the lactic acid yield increased greatly in the presence of Zn, Ni and activated carbon. Central composite response surface method (RSM) design experimentation was used to find the optimal concentrations of Zn, Ni, activated carbon and NaOH, which indicated that 0.02 g Zn, 0.03 g Ni, 0.07 g activated carbon and 2.5 mol/L NaOH were the optimal concentrations. Under this condition, the highest lactic acid yield was 42%, which was much higher than previous results using only NaOH (15%). The confirmatory experiments on lactic acid yield proved that the proposed model of lactic acid yield can accurately predict the lactic acid yield from cellulose.