Valorization of volatile fatty acids from the dark fermentation waste Streams-A promising pathway for a biorefinery concept

Abstract

In recent years, much attention has been directed towards the integration of dark fermentation process into a biorefinery concept to enhance the energetic gains, thereby improving the competitiveness of this process. The volatile fatty acids (VFAs) from dark fermentative H 2 -producing processes serve as precursors for the microbial synthesis of a broad spectrum of biotechnologically-important products such as biofuels and biocommodities. These products are desirable substrates for secondary bioprocesses due to their biodegradable nature and affordability. This short review discusses the use of acidogenic-derived VFAs in the production of value-added compounds such as polyhydroxyalkanoates (PHAs) alongside the microbial-based fuels (hydrogen, biogas, and electricity), and other valuable compounds (succinic acid, citric acid, and butanol). The review also highlights the strategies that have been used to enhance the extraction of VFAs from acidogenic effluents and other related waste streams. The application of novel enhancement techniques such as nanoparticles during VFAs recovery is also discussed in this work. Furthermore, the work highlights some of the recent advances in dark fermentationbased biorefinery, particularly the development of pilot-scale processes. Finally, the review provides some suggestions on the advancement of dark fermentation-based biorefineries using VFAs that are derived from acidogenic processes.

Hydrogen and Methane Production from Anaerobic Co-Digestion of Sorghum and Cow Manure: Effect of pH and Hydraulic Retention Time

“…This clearly suggests that the acute hydrogen production phase was mostly related to the accumulation of butyric acid. Regarding VFAs, the highest total amount was measured at pH 6.0 (16.79 g/L) as acetic and propionic acid were increased with increasing pH, indicating that the greatest VFA production occurred at pH 6.0, which is similar to other studies [47,48]. The acetic acid concentration at pH 6.0 was 9.54-fold higher than at pH 5.0, whereas the propionic acid concentration was 3.1-fold higher.…”

A Review on Factors Influencing the Fermentation Process of Teff (Eragrostis teff) and Other Cereal-Based Ethiopian Injera

“…Changes in the functional pH of the ethanol production process may utilize the main fermentation pathway. It is critical to maintain a pH range of 4.0 to 5.0, but if it exceeds this range, the production of by-products such as acetic and butyric acid may have eaten part of the substrates, lowering ethanol fermentation efficiency [ 72 ] as shown in Figure 5 .…”

Volatile Fatty Acid Production from Organic Waste with the Emphasis on Membrane-Based Recovery

“…Disposal methods, such as landfill composting and combustion, are limited by the availability of disposal sites, greenhouse gas emissions, and high energy consumption [1]. Organic waste is rich in organic and inorganic nutrients, is highly accessible, cost-effective and has a high moisture content [2]. Thus, is it considered as a potential substrate for bioenergy and biochemical production by anaerobic digestion.…”