Abstract:Studies on Undaria pinnatifida to date have mainly focused on its antioxidant, antitumor activities, while no reports are available on the endophytes from Undaria pinnatifida. In this study, fresh U. pinnatifida from Qingdao sea area was used to isolate and purify endophytes. A total of seven strains of endophytic fungi and five strains of endophytic bacteria were isolated, the acetylcholinesterase (AChE) inhibitory activity of each strain was evaluated by the 5,5-dithiobis-2-nitrobenzoic acid (DTNB) method, and active strains were identified. Strain QD-4 showed the highest AChE inhibitory activity and was identified, by physiological-biochemical characteristics and molecular biological techniques (using 16S rDNA sequencing), as Bacillus sp. and named as Bacillus sp. QD-4. The fermentation conditions were optimized using single-factor and orthogonal experiments with the inhibition rate on AChE in the fermentation broth as the activity indicator. The optimum carbon and nitrogen sources were identified as 5% starch and 1% peptone, respectively. The optimum fermentation conditions were as follows: fermentation time, 5 days; quantity of inoculum, 8%; initial substrate pH, 9.0; and culture temperature, 30 ℃. Under these conditions, the highest rate of AChE inhibition was 34.02% when the concentration of crude extract from fermentation broth was 20 mg/ml.
