# Recruiting a new strategy to improve levan production in Bacillus amyloliquefaciens

## TL;DR

Scientists improved levan production in a Bacillus strain by knocking out specific genes, achieving a significant increase in yield.

## Contribution

This is the first report showing that knocking out extracellular protease and TasA genes enhances levan production in microbes.

## Key findings

- The NK-Q-7 strain achieved 31.1 g/L levan, a 103% increase over the NK-ΔLP strain.
- The NK-Q-7 strain also showed a 94.1% increase in α-amylase production compared to the NK-ΔLP strain.
- Knocking out extracellular protease and TasA genes positively affects extracellular protein production.

## Abstract

Microbial levan is an important biopolymer with considerable potential in food and medical applications. Bacillus amyloliquefaciens NK-ΔLP strain can produce high-purity, low-molecular-weight levan, but production is relatively low. To enhance the production of levan, six extracellular protease genes (bpr, epr, mpr, vpr, nprE and aprE), together with the tasA gene (encoding the major biofilm matrix protein TasA) and the pgsBCA cluster (responsible for poly-γ-glutamic acid (γ-PGA) synthesis), were intentionally knocked out in the Bacillus amyloliquefaciens NK-1 strain. The highest levan production (31.1 g/L) was obtained from the NK-Q-7 strain (ΔtasA, Δbpr, Δepr, Δmpr, Δvpr, ΔnprE, ΔaprE and ΔpgsBCA), which was 103% higher than that of the NK-ΔLP strain (ΔpgsBCA) (15.3 g/L). Furthermore, the NK-Q-7 strain also showed a 94.1% increase in α-amylase production compared with NK-ΔLP strain, suggesting a positive effect of extracellular protease genes deficient on the production of endogenously secreted proteins. This is the first report of the improvement of levan production in microbes deficient in extracellular proteases and TasA, and the NK-Q-7 strain exhibits outstanding characteristics for extracellular protein production or extracellular protein related product synthesis.