Kinetic analysis of waste activated sludge hydrolysis and short-chain fatty acids production at pH 10

The accumulation of short-chain fatty acids （SCFAs）, a preferred carbon source for enhanced biological phosphorus removal microbes, was significantly improved when waste activated sludge （WAS） was fermented at pH 10. The kinetics of WAS hydrolysis and SCFAs production at pH 10 was investigated. It was observed that during WAS anaerobic fermentation the accumulation of SCFAs was limited by the hydrolysis process, and both the hydrolysis of WAS particulate COD and the accumulation of SCFAs followed first-order kinetics. The hydrolysis and SCFAs accumulation rate constants increased with increasing temperature from 10 to 35℃, which could be described by the Arrhenius equation. The kinetic data further indicated that SCFAs production at pH 10 was a biological process. Compared with the experiment of pH uncontrolled （blank test）, both the rate constants of WAS hydrolysis and SCFAs accumulation at 20℃ were improved significantly when WAS was fermented at pH 10.

Application of solvent pH under pressurized conditions using accelerated solvent extraction and green solvents to extract phytonutrients from wild berries

Berry fruits are known as“superfoods”due to health benefits associated with the high content of bioactive compounds or phytonutrients.Organic extraction solvents are fundamentally volatile compounds acquired from non-renewable resources,i.e petroleum-based solvents are presumed to be harmful to both human health and the environment.Owing to the new emphasis on environmental and safety protections and the development of green chemistry,finding alternative solvents to replace the organic ones has recently become a major concern.Indeed,there is a great interest in the scientific community to develop a suitable green approach to allow the extraction and recovery of the bioactive phytonutrients from berry sources for applications in improving human health and nutrition.In this study,the phytonutrient composition of three popular wild berries:blueberry(Vaccinium angustifolium),partridgeberry(Vaccinium vitis-idaea L.)and Rosehipberry(Rosa canina),were evaluated following extraction using biphasic green solvents at pH 2.5,7.0,and 11.5 under pressurized conditions using Accelerated Solvent Extraction(ASE)system.The total phenolic content and composition,antioxidant activity,vitamin and mineral content of the berry extracts were evaluated using Folin-Ciocalteu assay,Ferric Reducing Antioxidant Power Assay(FRAP),Ultra-High-pressure Liquid Chromatography-Mass Spectrometry(UHPLC-MS)and inductively coupled plasma-mass spectrometry(ICP-MS),respectively.The highest total antioxidant activity(p≤0.05)and phenolic content were observed in rosehip berry followed by blueberry and partridgeberry in the hydroethanolic extracts at pH 11.5.Nevertheless,the highest extraction efficiency of total fat-soluble vitamins(FSV)and total B vitamins were also observed in the hydroethanolic extract at pH 11.5.Both in rosehipberry and partridgeberry the highest vitamin C content was observed in hydroethanolic extract at pH 11.5,whereas in blueberry it was observed in the pH 2.5 hydroethanolic extract.In the present study,results demonstrated that using the green solvent system(hydroethanolic,70:30 v/v)at alkaline pH(11.5)as a pressurized fluid in the ASE system provided significant recovery of phytonutrients from wild berries.This green environmentally friendly system of extraction could represent a suitable alternative for the preparation of food grade or green solvent-based extracts for applications in the food and nutraceutical industry.