Biosynthesis of polyhydroxyalkanoate from food waste oil by Pseudomonas alcaligenes with simultaneous energy recovery from fermentation wastewater.

Bioconversion of food waste oil (FWO) into biodegradable plastic is a promising method for converting waste into high-value products. In this study, a strain (Pseudomonas sp. H3) was isolated for polyhydroxyalkanoate (PHA) synthesis from FWO. After 72 h of cultivation with 20 g/L of FWO, the high cell dry weight (CDW) of 3.6 g/L, PHA yield of 2.4 g/L, and PHA content of 65 wt% were obtained under the optimal temperature (25 °C) and inoculum amount (6% (v/v)). Fed-batch fermentation was conducted in a 5 L bioreactor with a maximum CDW of 16 g/L, PHA content of 54 wt%, and PHA productivity of 0.23 g/(L·h) after 36 h. The PHA had a molecular weight of 54 782 Da and a low polydispersity index of 1.41 with glass transition, melting, and degradation temperatures of -20 °C, 34 °C, and 210 °C, respectively. To further utilize the wastewater after PHA production, anaerobic digestion was employed for CH4 production, and the CH4 yield was 284 mL/g volatile solids. Microbial community analysis showed that the abundance of acetate-oxidizing bacteria and Methanobacterium significantly increased during anaerobic digestion. This study describes a new strain for the economical synthesis of biodegradable plastics and presents a novel framework for fully utilizing FWO with the production of PHA and CH4.

Factors of Importance for Arsenic Migration/Separation under Coffee-Ring Effect on Silver Nanofilms.

Surface-enhanced Raman spectroscopy (SERS) has been recognized as a promising analytical technique owing to its merit of nondestructive and fast detection capabilities. However, SERS usually suffers signal interferences from different analytes or a complicated matrix. Separation is an effective approach to solve the signal interference in the application of SERS. It was proposed that two concentric coffee rings could serve as a simple separation platform; however, there are still many questions to be answered for in-depth understanding. In this study, critical parameters during the formation of two concentric coffee rings are characterized for a better understanding of this phenomenon, including surface tension, surface morphology, and surface energy. Two arsenicals, including arsenate (AsV) and cacodylic acid (DMAV), are chosen to study the arsenicals' separation/migration mechanism due to their significant difference in chemical properties. In the typical coffee ring, these two arsenicals have signal interference and only DMAV is detected via SERS; however, they are detected along the radius of the two concentric coffee rings. The distribution of arsenicals on the two concentric coffee rings is further verified by the chromatographic method. Under this simple platform, interactions between the arsenicals and the surface of the silver nanofilm are pivotal to their migration/separation. By surface modification of silver nanofilm with small molecules, the surface polarity and surface ζ potential are manipulated. The signal dynamics of these two arsenicals are studied on these modified silver nanofilms. It is clear that the electrostatic interaction plays a more important role than the polarity in the arsenicals' migration. This study reveals the mechanism of small molecule migration/separation in the two concentric coffee rings and provides insights for future study of employing this simple platform.