Bioinspired Lipase Immobilized Membrane for Improving Hesperidin Lipophilization.

Lipophilization is a promising way to improve the bioavailability of flavonoids. However, the traditional enzymatic esterification methods are time-consuming, and present low yields and purity. Herein, a novel membrane-based lipophilization technology-bioinspired lipase immobilized membranes (BLIMs), including CAL-B@PES, CAL-B@PDA/PES and GA/CAL-B@PDA/PES- were fabricated to improve the antioxidant flavanone glycoside hesperidin lipophilization. Via reverse filtration, PDA coating and GA crosslinking, Candida antarctica lipase B (CAL-B) was stably immobilized on membrane to fabricate BLIMs. Among the three BLIMs, GA/CAL-B@PDA/PES had the greatest enzyme activity and enzyme loading, the strongest tolerance of changes in external environmental conditions (temperatures, pH, heating time, storage time and numbers of cycles) and the highest hesperidin esterification efficiency. Moreover, the optimal operating condition for GA/CAL-B@PDA/PES fabrication was the CAL-B concentration of 0.36 mg/mL, operation pressure of 2 bar, GA concentration of 5% and crosslinking time of 1 h. Afterwards, the hesperidin esterification process did not affect the micromorphology of BLIM, but clearly improved the BLIM permeability and esterified product efficiency. The present study reveals the fabrication mechanism of BLIMs and offers insights into the optimizing strategy that governs the membrane-based lipophilization technology process.

Structure and stability analysis of antibacterial substance produced by selenium enriched Bacillus cereus BC1.

Microorganisms can produce many antibiotics against bacteria and fungi, which have been used as a potential choice of new antibiotics. In this paper, we studied the characteristics of antibacterial substances by Bacillus cereus BC1. The results showed that the acid-precipitated substance played the main role in antibacterial activity, and further characterization indicated that the antibacterial substance might be a lipopeptide substance. Then the antibacterial spectrum suggested that the antibacterial substance had an inhibitory effect on Gram-positive bacteria and fungi, while selenium-riched antibacterial substance of Bacillus cereus BC1 could significantly enhance the inhibition. Then the morphological effects of the antibacterial substance to indicator bacteria were determined. The effects of different treatment methods on the stability of antibacterial substances were studied and the results showed that the antibacterial substance was stable to heat, ultrasonic, and ultraviolet treatment, and their antibacterial activity would not be greatly affected. However, they were sensitive to pepsin. The optimum pH range of antibacterial activity was 3-5. This study may contribute to reusing the fermentation supernatant often discarded in the previous fermentation process. At the same time, the lipopeptide antibacterial substance extracted from the fermentation broth of selenium-enriched Bacillus cereus BC1 can be used in the development of antibiotics and biopesticides, and open up a new way for the control of plant diseases.