Statistical Optimization for Succinic Acid Production from E. Coli in a Cost-Effective Medium

Characterization of a β-glucosidase from Paenibacillus species and its application for succinic acid production from sugarcane bagasse hydrolysate

In this study, a β-glucosidase from Paenibacillus sp. M1 was expressed in E. coli BL21(DE3), purified and characterized. The specific activity of purified BglA was 137.64U·mg^-1 protein with optimal temperature and pH of 50°C and 6.0. Furthermore, BglA shows excellent adaption to various environmental factors such as temperature, pH and metal ions. Engineered E. coli Suc260 was further reconstructed by overexpressing the β-glucosidase for achieving direct cellobiose utilization, which could efficiently utilize the pretreated sugarcane bagasses hydrolysate (SBH) consisting of 25.30g·L^-1 cellobiose, 9.70g·L^-1 glucose, 5.90g·L^-1 arabinose and 7.10g·L^-1 xylose. As a result, 26.50g·L^-1 and 24.30g·L^-1 succinic acid were produced by strain Suc260(pTbglA) from cellobiose and SBH with corresponding yields of 88.30% and 89.20% using dual-phase fermentation, respectively. This study indicated that incomplete enzymatic hydrolysate of SCB will be a potential feedstock for succinic acid production.

Statistical optimization for the production of recombinant cold-adapted superoxide dismutase in E. coli using response surface methodology

Cold-adapted superoxide dismutase (SOD) with higher catalytic activity at lower temperature has great amount of applications in many aspects as an industrial enzyme. The application of recombinant enzyme in gene engineering and microbial fermentation technology is an effective way to obtain high-yield product. In this study, to obtain the recombinant SOD in E. coli (rPsSOD) with the highest activity, the Box-Behnken design was first applied to optimize the important parameters (lactose, tryptone and Tween-80) affecting the activity of rPsSOD. The results showed that the optimal fermentation conditions were Tween-80 (0.047%), tryptone (6.16 g/L), lactose (11.38 g/L). The activity of rPsSOD was 71.86 U/mg (1.54 times) as compared with non-optimized conditions. Such an improved production will facilitate the application of the cold-adapted rPsSOD.

Production, characterization, and properties of sophorolipids from the yeast Candida bombicola using a low-cost fermentative medium

The yeast Candida bombicola produces biosurfactant with properties akin to those of sophorolipid (SL) group of compounds. In the present work, the yeast was shown to produce 63.7 g l(-1) SL when grown on a cheap fermentative medium containing sugarcane molasses, yeast extract, urea, and soybean oil. The partially purified SL was characterized and confirmed by Fourier-transform infrared (FT-IR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR) and liquid chromatography-mass spectroscopy (LC-MS) analysis. The critical micelle concentration (CMC) and minimum surface tension of the produced SL in aqueous solution were found to be 59.43 mg l(-1) and 34.15 m Nm(-1), respectively. The emulsification activity and stability with kerosene oil and organic solvents viz. xylene, benzene, and hexadecane were also tested using the produced SL, which yielded better results compared to those reported in the literature.