Volatile fatty acids production from protease pretreated Chlorella biomass via anaerobic digestion.

Volatile fatty acids (VFAs) produced via anaerobic digestion (AD) are regarded as a low cost production process of building blocks of interest for the chemical industry. In this study, VFAs and methane production were assessed in batch reactors at different temperature ranges (psychrophilic 25°C, mesophilic 35°C, thermophilic 50°C) and different pH values (5.5 and 7.5) using protease pretreated Chlorella sp. biomass as substrate. Acetic acid and propionic acid were the most abundant products (up to 73% of the total VFAs) during the first days independently of the conditions. VFAs concentration decreased over time as methane was produced after a lag phase of 7-10 days. Results showed that best conditions for VFAs production were mesophilic temperature ranges (35°C) at neutral initial pH values (7.5), and psychrophilic temperature ranges (25°C) at low initial pH values (5.5) which resulted in a conversion of the initial COD into VFAs of 48%, respectively.