Green synthesis of isomaltulose from cane molasses by Bacillus subtilis WB800-pHA01-palI in a biologic membrane reactor

- Sucrose isomerase was firstly expressed in B. subtilis WB800.
- Cane molasses as low-cost food waste was firstly used to isomaltulose production.
- B. subtilis WB800, a GRAS microbe, was firstly used for isomaltulose synthesis.
- BMR system exhibited great operational stability for isomaltulose production.

A green process and environmentally benign process is highly desirable in the development of enzymatic catalysis. In this work, the shuttle plasmid pHA01 was constructed and the sucrose isomerase (SIase) was expressed in Bacillus subtilis WB800. The optimal nitrogen and carbon sources for SIase expression were yeast extract (15 g/L) and un-pretreated cane molasses (UCM, 20 g/L), respectively. After the UCM fed, the whole cell activity reached 5.2 U/mL in a 7.5 L fermentor. Optimum catalytic temperature and pH of whole cell were 35 °C and 5.5, respectively. Although the biologic membrane reactor (BMR) system consecutively worked for 12 batches, the sucrose conversion remained higher than 90%, indicating the BMR system had a greater operational stability. Furthermore, isomaltulose production using the BMR system with low-cost cane molasses as its substrate not only reduces the production cost and mediates environmental pollution, but also solves the genetic background problem of the non-food-grade strains.