Investigations in ultrasound-assisted anticoagulant production by marine Bacillus subtilis ZHX

Effect of ultrasound on the stability of partial nitrification: Under the interference of aeration rate

The fluctuation of dissolved oxygen is one of the primary cause of disruptions to the consistent operation of partial nitrification, and the level of dissolved oxygen is mainly controlled by the aeration rate. This study investigated the influence of ultrasonic treatment on the stability of partial nitrification of activated sludge under different aeration conditions. After being treated with ultrasound (energy density = 0.20 W·mL-1, treatment time = 10 min), partial nitrification process operated stably for 67 days, with the nitrite accumulation rate above 83.89 %. The effluent contained 42.50 mg·L-1 of nitrite, much higher than the control reactor (0.30 mg·L-1). The gap between the specific ammonia and nitrite oxidation rates widened continuously as the aeration rate increased, and nitrite-oxidizing bacteria activity did not recover even under conditions with a very high oxygen content. Further analysis showed that ultrasonic treatment had obvious stripping effect on excess extracellular polymeric substances (EPS), especially loosely bound EPS and protein. Additionally, long-term ultrasonic treatment promoted the enrichment of Nitrosomonas and strongly inhibited Nitrotoga. Based on these findings, it appears that under conditions of high aeration rate, ultrasound effectively suppress the recovery of Nitrotoga activity and improve the stability of partial nitrification.

Improvement of the Biosynthesis of Resveratrol in Endophytic Fungus (Alternaria sp. MG1) by the Synergistic Effect of UV Light and Oligomeric Proanthocyanidins

Resveratrol, a natural polyphenol compound with multiple bioactivities, is widely used in food and pharmaceutical industry. Endophytic fungus Alternaria sp. MG1, as a native producer of resveratrol, shows increasing potential application. However, strategies for improvement of the biosynthesis of resveratrol in this species are still scarce. In this study, different elicitors were used to investigate their effect on the biosynthesis of resveratrol in MG1 and the induction mechanism. Ultrasound and sodium butyrate had no effect and slight inhibition on the resveratrol production and related gene expression, respectively. UV radiation and co-culture with Phomopsis sp. XP-8 significantly promoted the biosynthesis of resveratrol with the highest production (240.57μg/l) coming from UV 20min. Co-culture altered the profiles of secondary metabolites in MG1 by promoting and inhibiting the synthesis of stilbene and lignin compounds, respectively, and generating new flavonoids ((+/-)-taxifolin, naringin, and (+)-catechin). Oligomeric proanthocyanidins (OPC) also showed an obviously positive influence, leading to an increase in resveratrol production by 10 to 60%. Two calcium-dependent protein kinases (CDPK) were identified, of which CDPK1 was found to be an important regulatory factor of OPC induction. Synergistic treatment of UV 20min and 100μm OPC increased the production of resveratrol by 70.37% compared to control and finally reached 276.31μg/l.