Recovery of thuringiensin with cetylpyridinium chloride using micellar-enhanced ultrafiltration process

摘要

A cationic cetylpyridinium chloride (CPC) surfactant-based micellar-enhanced ultra-filtration (MEUF) process was used to recover thuringiensin from the supernatant of Bacillus thuringiensis fermentation broth. Several different strategies of manipulating process variables, such as ionic strength, pH, CPC concentration, micelle formation temperature and membrane pore size, were investigated. It was found that CPC concentration and membrane pore size were 2 major factors to the increase of thuringiensin recovery, while ionic strength and pH adjustments were not necessary and micelle formation temperature was not important within the temperature range studied. Finally, a novel 2-step MEUF processing scheme was developed which includes microfiltrationand 2-step ultrafiltration (UF) processes. Thuringiensin recovery up to 94.6% was attained when an initial CPC concentration of 4% (w/v) and UF membrane of molecular weight cutoff (MWCO) of 3000 was used in conjunction with the previous UF process usinga MWCO 30 000 membrane. The bioassay results showed that the spray-dried thuringiensin with CPC was more toxic to Musca domestica larvae than without CPC. At 0.625 ppm, thuringiensin with CPC addition achieved 62.5% mortality after 5 days, whereas 35.0%mortality was achieved without CPC addition. The results demonstrate that CPC not only facilitates thuringiensin recovery, but also improves the insecticidal effect.