Initial-alkaline motivated fermentation of fine-sieving fractions and its effect on properties of cellulosic components

Abstract

Exploration of value-added products from wastewater treatment plants (WWTPs) was promising for its sustainable development. This study simultaneously addressed the possibility of volatile fatty acids (VFAs) production boost and cellulosic components recovery from fine-sieving fractions (FSF) under initial alkaline conditions. The step utilization of FSF was relatively untapped in similar literatures. The effect of different initial pH values with 8.5, 9.5 and 10.5 (defined as F-8.5, F-9.5 and F-10.5) on fermentation performance were investigated. Then, the fermentation residues were collected to evaluate the changes in chemical structure and thermodynamic properties by fourier transform infrared spectroscopy (FTIR) and thermo-gravimetric (TG) analysis. Furthermore, analysis of the changes in microbial community structure and the interaction between functional genus and performance parameters were undertaken by high throughput sequencing and canonical correspondence analysis (CCA). Results showed that F-10.5 obtained the highest VFAs yields of 234 mg/g VSS, due to efficient polysaccharides release and inhibited methane production. However, high alkaline intensity caused proteins denaturation. Acidogenesis kinetics suggested that the fermentation rate was chemical-dominated. Although crystalline structure was more disordered with increasing alkalinity, the weight loss was lower than 2.5%, making it possible to recover cellulose from fermented residues. Interaction between functional genus and performance parameters revealed the microbial mechanism during the alkaline fermentation. Consequently, the initial-alkaline motivated fermentation was proved to be a promising technology in value-added products recovery to be cost economic, energy positive and environmental friendly.