Lactic acid from mixed food waste fermentation using an adapted inoculum: Influence of pH and temperature regulation on yield and product spectrum

Waste to Wealth: The power of food-waste anaerobic digestion integrated with lactic acid fermentation

“…A growing body of recent key literature has explored the upstream fermentation of FW for LA followed by the downstream utilisation of the fermentation residues in AD for biogas production, aiming to generate greater financial feasibility (Kim et al, 2016;Demichelis et al, 2017;Bastidas-Oyanedel and Schmidt, 2018;Bühlmann et al, 2021;Bühlmann et al, 2022a;Bühlmann et al, 2022b). The two processes can be closely integrated to synergistically improve their performance.…”

“…The sequential process by which AD breaks down biomass to biogas is complex and generates a variety of intermediate products, which if co-produced with biogas/power and digestate, could boost revenue from AD. LA is a promising high-value intermediate produced during the pre-fermentation stage of two-stage AD and has been the focus of a few recent studies (Kim et al, 2016;Bastidas-Oyanedel and Schmidt, 2018;Demichelis et al, 2018;Bühlmann et al, 2021;Bühlmann et al, 2022a;Bühlmann et al, 2022b;Chenebault et al, 2022). LA (C 3 H 6 O 3 ) is a three-carbon organic acid which is generally sold as an 88 wt% solution which is expected to experience significant market growth to 1,960 kton by 2024/ 2025 valued at USD 9.8 billion (Alves de Oliveira et al, 2018;Presswire, 2018).…”

“…As LAB struggle to ferment substrates composing of complex polymers, pre-treatment processes have shown their benefit, for example, with pulp mill residue (de Oliveira Moraes et al, 2016), corn stover (Ahring et al, 2016), and sugarcane bagasse (Wischral et al, 2019). Though FW is inherently relatively biodegradable, having been shown to produce substantial LA from direct fermentation (e.g., 0.46 gLA•gTS −1 (Tang et al, 2016), 0.18 gLA•gTS −1 (high TS content) (Yousuf et al, 2018), 0.55 gLA•gVS −1 (Bühlmann et al, 2022b), and 0.42 gLA•gVS −1 (Wang et al, 2021)), application of pre-treatment methods to FW have been shown to benefit LA fermentation by improving the final LA yield (Kim K. I. et al, 2003;Kwan et al, 2016;Pleissner et al, 2016;Demichelis et al, 2017;Ahmad et al, 2020).…”

“…Though this does not pose a problem for AD, it can be a significant risk to the economics of LA fermentation. Many fermentation systems with optimised process conditions (e.g., pH, temperature, HRT, and OLR) tend to selectively promote LAB and LA production (Kim et al, 2016;Tang et al, 2016;Bühlmann et al, 2022b). However, FWs contain a variety of alternate bacteria, and are naturally enriched with many LAB (Kim et al, 2016), which may compete with target strains for substrate, reducing LA yields and selectivity.…”

“…Biorefineries, analogous to oil refineries, produce a range of fuels, chemicals, and materials, but use biomass as their source material instead of fossil fuels (Figure 1). AD has the potential to produce a variety of high value biomaterials, biochemicals, and biofuels (Moraes et al, 2014;Sawatdeenarunat et al, 2016;Bastidas-Oyanedel and Schmidt, 2018) with lactic acid (LA) being of particular interest in recent research (Kim et al, 2016;Demichelis et al, 2017;Demichelis et al, 2018;Bühlmann et al, 2021;Bühlmann et al, 2022a;Bühlmann et al, 2022b). LA is a high-value chemical utilised in a variety of industries, including the food and pharmaceutical industries, with modern applications aiming to produce biodegradable…”