Optimization of l-arginine purification from Corynebacterium crenatum fermentation broth.

l-Arginine has many special physiological and biochemical functions, with wide applications in the food and pharmaceutical industry. Few studies on the purification of l-arginine from fermentation broth have been conducted; however, none of them were systematic enough for industrial scale-up. Therefore, it is necessary to develop a highly efficient and systematic process for the purification of l-arginine from fermentation broth. In this study, we screened out a cation exchange resin, D155, having high exchange capacity, high selectivity, and easy elution capacity, and analyzed its adsorption isotherm, thermodynamics, and kinetics using different models. Further, the process parameters of fixed-bed ion exchange adsorption and elution were optimized, and the penetration curve during the operation was modeled. Based on the fixed-bed ion-exchange parameters, a 30-column continuous ion-exchange system was designed, and the flow velocity in each zone was optimized. Finally, to obtain a high purity of l-arginine, the purification tests were conducted using anion exchange resin 711, and an l-arginine yield of 99.1% and purity of 98.5% was obtained. This effective and economical method also provides a promising strategy for separation of other amino acids from the fermentation broth, which is of great significance to the l-arginine fermentation industry.

Heterologous expression and characterization of a new heme-catalase in Bacillus subtilis 168.

Reactive oxygen species (ROS) is an inherent consequence to all aerobically living organisms that might lead to the cells being lethal and susceptible to oxidative stress. Bacillus pumilus is characterized by high-resistance oxidative stress that stimulated our interest to investigate the heterologous expression and characterization of heme-catalase as potential biocatalyst. Results indicated that recombinant enzyme significantly exhibited the high catalytic activity of 55,784 U/mg expressed in Bacillus subtilis 168 and 98.097 µmol/min/mg peroxidatic activity, the apparent K m of catalytic activity was 59.6 ± 13 mM with higher turnover rate (K cat = 322.651 × 10(3) s(-1)). The pH dependence of catalatic and peroxidatic activity was pH 7.0 and pH 4.5 respectively with temperature dependence of 40 °C and the recombinant heme-catalase exhibited a strong Fe(2+) preference. It was further revealed that catalase KatX2 improved the resistance oxidative stress of B. subtilis. These findings suggest that this B. pumilus heme-catalase can be considered among the industrially relevant biocatalysts due to its exceptional catalytic rate and high stability and it can be a potential candidate for the improvement of oxidative resistance of industrially produced strains.