Isolation and characterization of Paenibacillus peoriae JC-3jx from Dendrobium nobile.

Dendrobium is a rich source of high-value natural components. Endophytic fungi are well studied, yet bacteria research is limited. In this study, endophytic bacteria from Dendrobium nobile were isolated using an improved method, showing inhibition of pathogens and growth promotion. JC-3jx, identified as Paenibacillus peoriae, exhibited significant inhibitory activity against tested fungi and bacteria, including Escherichia coli. JC-3jx also promoted corn seed rooting and Dendrobium growth, highlighting its excellent biocontrol and growth-promoting potential.

Genome shuffling and high-throughput screening of Brevibacterium flavum MDV1 for enhanced L-valine production.

L-valine is an essential branched-amino acid that is widely used in multiple areas such as pharmaceuticals and special dietary products and its use is increasing. As the world market for L-valine grows rapidly, there is an increasing interest to develop an efficient L-valine-producing strain. In this study, a simple, sensitive, efficient, and consistent screening procedure termed 96 well plate-PC-HPLC (96-PH) was developed for the rapid identification of high-yield L-valine strains to replace the traditional L-valine assay. L-valine production by Brevibacterium flavum MDV1 was increased by genome shuffling. The starting strains were obtained using ultraviolet (UV) irradiation and binary ethylenimine treatment followed by preparation of protoplasts, UV irradiation inactivation, multi-cell fusion, and fusion of the inactivated protoplasts to produce positive colonies. After two rounds of genome shuffling and the 96-PH method, six L-valine high-yielding mutants were selected. One genetically stable mutant (MDVR2-21) showed an L-valine yield of 30.1 g/L during shake flask fermentation, 6.8-fold higher than that of MDV1. Under fed-batch conditions in a 30 L automated fermentor, MDVR2-21 accumulated 70.1 g/L of L-valine (0.598 mol L-valine per mole of glucose; 38.9% glucose conversion rate). During large-scale fermentation using a 120 m3 fermentor, this strain produced > 66.8 g/L L-valine (36.5% glucose conversion rate), reflecting a very productive and stable industrial enrichment fermentation effect. Genome shuffling is an efficient technique to improve production of L-valine by B. flavum MDV1. Screening using 96-PH is very economical, rapid, efficient, and well-suited for high-throughput screening.

Molecular cloning and overexpression of an endo-ß-1,4-xylanase gene from Aspergillus niger in industrial Saccharomyces cerevisiae YS2 strain.

The aim of this study was to endow an industrial strain of Saccharomyces cerevisiae with the ability to overexpress the xylanase by constructing a homology-driven integration vector. The total mRNA from a xylanase-producing strain of Aspergillus niger IME-216 was extracted and used as the template for the production of endo-ß-1,4-xylanase cDNA by reverse transcription. The fusion fragment containing the phosphoglycerate kinase promoter, α-factor signal peptide, xylanase gene encoding the mature peptide, and CYC1 terminator was first generated by overlap extension polymerase chain reaction. Then, the vector pUPX was constructed by inserting the fusion fragment into the S. cerevisiae plasmid pUG6. Then, A 2.2-kb rDNA sequence was further cloned and attached to the SalI-digested pUPX to obtain the integration plasmid pUPXR. The pUPXR was linearized by KpnI, transformed into the industrial strain S. cerevisiae YS2 using the lithium acetate method and integrated into the S. cerevisiae chromosome. The maximum yield of the recombinant xylanase produced by the engineered S. cerevisiae strain YS2_2 was 74.8 U per microliter, which was about 1.5-fold higher than the original 50 U per microliter by Aspergillus niger IME-216 strain under the flask culture at 28 °C for 72 h. The findings of our study can be used for further development of industrial S. cerevisiae strain for producing interested enzymes, or improving the achievement of metabolism, for example, simultaneous fermentation of glucose and xylose to producing bioethanol.