Effects of culture condition and nutrition on the co-production of microbial oil and exopolysaccharide by Sporidiobolus pararoseus JD-2

Microbial oil has been gaining considerable attention from researchers recently as renewable and ecofriendly oil and its potential as feedstock for food industry and biodiesel industry. In this context, we have earlier demonstrated production of microbial oil and exopolysaccharide (EPS) from the yeast Sporidiobolus pararoseus JD-2. In this study, we explored increasing its production by optimizing the culture condition and nutrition. As expected, culture temperature and dissolved oxygen (DO) are the contributing factors for co-producing microbial oil and EPS, in which 28? and lower quantum (i.e., 30 mL/500 mL) show the best conditions in shake-flasks fermentation. By contrast, the initial pH from 4 to 8 has no obvious effect on producing microbial oil and EPS. In addition, the culture nutrition (i.e., carbon/nitrogen source) were also discussed, and indicating that 20 g/L of corn steep liquor and 60 g/L of glucose are beneficial to produce microbial oil and EPS (i.e., 34.1±1.2 g/L and 11.5±0.2 g/L, respectively). Meanwhile, the residue glucose should be maintained at 20 g/L, in which the highest production of microbial oil and EPS was obtained (i.e., 34.6±1.7 g/L and 11.7±0.8 g/L, respectively). The biomass, microbial oil and EPS were further increased during optimizing the DO level, which reached to 67.8±2.1 g/L, 34.7±0.6 g/L and 11.8±0.5 g/L during maintaining DO level at 20-30%, respectively. The results suggest that appropriate culture condition and nutrition considerably improve the fermentation performance of S. pararoseus JD-2 and significantly increase co-production of microbial oil and EPS (by 11.2 and 8.3%, respectively) compared to the un-optimized fermentation.

Expression,purification and bioinformatics analysis of PE＿PGRS35 protein of Mycobacterium tuberculosis H37Rv strain / 中国生物制品学杂志

@#Abstract： Objective To clone PE_PGRS35 gene of Mycobacterium tuberculosis（MTB），construct recombinant vector pET28a⁃PE_PGRS35，express and purify the PE_PGRS35 protein of MTB H37Rv heterologously，and explore a new target against MTB after bioinformatics analysis. Methods The PE_PGRS35 coding gene was amplified by PCR and used to construct the expression vector pET28a⁃PE_PGRS35 by recombinant cloning technology，which was transformed to E. coli BL21（DE3）after successful sequencing and induced by using IPTG. The obtained PE_PGRS35 protein was purified by Ni column affinity chromatography and analyzed by bioinformatics. Results The pET28a⁃PE_PGRS35 prokaryotic expression vector was constructed correctly as identified by sequencing. The PE_PGRS35 protein was mainly expressed in the form of inclusion bodies，with a relative molecular mass of about 53 000 and a purity of 90%. Bioinformatics analysis showed that PE_PGRS35 protein was an acid⁃labile protein，with main secondary structure of β⁃sheet and random coil，and no transme⁃ mbrane region，which was presumed to be an extramembrane protein with 39 phosphorylation sites and two conserved domains. Total 10 proteins，including Rv1769，PPE8，PPE64，PPE54，PPE24，PPE16，PPE35，PPE6，PPE28 and PE2， interacted with PE_PGRS35 protein. Conclusion PE_PGRS35 protein with high purity was successfully obtained，which provided a reference for the further development of new targets for drugs against MTB.