Genome shuffling of Propionibacterium shermanii for improving vitamin B12 production and comparative proteome analysis.

Genome shuffling is an efficient approach for the rapid improvement of microbial phenotype. Here we improved vitamin B12 production of Propionibacterium shermanii by genome shuffling based on inactivated protoplast fusion. A genome shuffling strain with titer of vitamin B12 of 2.85 mgl(-1), named Propionibacterium shermanii-F2-3, was obtained. The genome shuffled strain produced about 61% improvement of vitamin B12 over the parent strain after 96 h. Comparative analysis of proteome profile was conducted between Propionibacterium shermanii 17 and F2-3. The expression levels of 38 proteins varied significantly in the genome shuffled strain compared with those in the parent strain. Of these proteins, 22 proteins were up-regulated, 16 proteins were down-regulated. Of the up-regulated proteins, 6 proteins (glutaminyl-tRNA synthetase (GlnS), Delta-aminolevulinic acid dehydratase (HemB), methionine synthase (Meth), riboflavin synthase (RibE), phosphofructo kinase (PfkA) and isocitrate dehydrogenase (Icd) is involved in the vitamin B12 biosynthesis pathway. They may be the key enzymes of vitamin B12 biosynthesis.