Microbial communities for valorizing biomass using the carboxylate platform to produce volatile fatty acids: A review.

The carboxylate platform employs a diverse microbial consortium of anaerobes in which the methanogens are inhibited. Nearly all biomass components are digested to a mixture of C1-C8 monocarboxylic acids and their corresponding salts. The methane-arrested anaerobic digestion proceeds readily without needing to sterilize biomass or equipment. It accepts a wide range of feedstocks (e.g., agricultural residues, municipal solid waste, sewage sludge, animal manure, food waste, algae, and energy crops), and produces high product yields. This review highlights several important aspects of the platform, including its thermodynamic underpinnings, influences of inoculum source and operating conditions on product formation, and downstream chemical processes that convert the carboxylates to hydrocarbon fuels and oxygenated chemicals. This review further establishes the carboxylate platform as a viable and economical route to industrial biomass utilization.

Arrested methanogenesis digestion of high-strength cheese whey and brewery wastewater with carboxylic acid production.

A new anaerobic digestion process based on arrested methanogenesis (AM) was developed to treat high-strength cheese whey and brewery wastewater with simultaneous carboxylic acid production. This study specifically determined the links between wastewater characteristics, microbial community structure, and the operation of AM digesters at the bench scale. The highest total carboxylic acids concentration (78 g/L) was achieved after 15 days under batch condition at 40 °C and near-neutral pH. Lactate conversion to chain-elongated volatile fatty acid was observed. Under fed-batch conditions, the highest total acid productivity was 16 g/(Lliq·d) with substrate conversion of 0.66 g CODdigested/g CODfed at hydraulic residence time (HRT) of 4 days. Fed-batch digestion with biomass recycling resulted in a 2-fold increase in VFAs concentration (30 g/L) and a higher diversity in the microbial consortia. Experimental results show that highly efficient, robust, and productive community structure was established for sustainable carboxylate production from widely varying high-strength wastewaters.

Impact of mono- and disubstitution on the colorimetric dynamic covalent switching chalcone/flavanone scaffold.

The effect of aryl substitution on various aspects of the interconversion of ortho-hydroxychalcones and flavanones has been studied using multiple spectroscopic techniques. Derivatization of the core scaffold predictably alters the midpoint pH of this equilibration process suggesting its viability for application as a functional colorimetric molecular switch.

Towards a dynamic covalent molecular switch: substituent effects in chalcone/flavanone isomerism.

Chalcone/flavanone interconversion occurs facilely under aqueous alkaline conditions making it a promising scaffold for the development of a covalent molecular switch. In this study, a single methoxy substituent is shown to have a significant impact on the equilibrium dynamics of this reaction; this impact is dependent on the site of substitution.