•A new electrochemically active bacterium identified as Kocuria rhizophila was first isolated.•Direct electron transfer was proved to be the main exoelectrogenic mechanism for MFCs.•Lysozyme-treated cells achieved the highest power density of 206 mW/m2 that increased 1.75 times.•It offers a novel Gram-positive bacterium for power production in MFCs.•It proved chemical treatment was a feasible strategy to improve bioelectrons transfer.It is certainly an important research area to discovery new exoelectrogens for microbial fuel cells (MFCs), and how to effectively manipulate its cell property to improve power performance is still a great challenge. In this study, a new electrochemically active bacterium phylogenetically related to Kocuria rhizophila was first isolated and found electrogenic in MFCs, which was identified through the combination methods of molecular biology, physiological, biochemical and morphological characteristics. The MFCs inoculated with this strain generated power from a wide variety of substrates, reached a maximum power density of 75 mW/m2 in the substrate of 1 g/L glucose. And the electron transfer mechanism was confirmed to be dominantly direct biofilm mechanism. Chemical treatment with five reagents was verified to be a feasible strategy to improve the power density of MFCs, increasing approximately 1.75 fold at most after treated with lysozyme. This enhancement was contributed to the significant enhancement on cell permeability, cell membrane fluidity and Coenzyme Q10 (the electron carrier). Thus this work offered a novel Gram-positive electrogenic bacterium and proved chemical treatment was a feasible strategy to improve electron transfer for application in MFCs.

Improvement of natamycin production by Streptomyces gilvosporeus ATCC 13326 was performed by recursive protoplast fusion in a genome-shuffling format. After four rounds of genome shuffling, the best producer, GS 4-21, with genetic stability was obtained and its production of natamycin reached 4.69 ± 0.05 g/L in shaking flask after 96 h cultivation, which was increased by 97.1% and 379% in comparison with the highest parental strain pop-72Ar07 and the initial strain ATCC 13326, respectively. Compared with the initial strain ATCC 13326, the recombinant GS 4-21 presented higher polymorphism. Fifty-four proteins showed differential expression levels between the recombinant GS 4-21 and initial strain ATCC 13326. Of these proteins, 34 proteins were upregulated and 20 proteins were downregulated. Of the upregulated proteins, one protein, glucokinase regulatory protein, was involved in natamycin biosynthesis. This comprehensive analysis would provide useful information for understanding the natamycin metabolic pathway in S. gilvosporeus.