From Upstream to Purification: Production of Lactic Acid from the Organic Fraction of Municipal Solid Waste
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ORIGINAL PAPER
From Upstream to Purification: Production of Lactic Acid from the Organic Fraction of Municipal Solid Waste José Pablo López‑Gómez1 · Peter Unger1 · Roland Schneider1 · Joachim Venus1 Received: 30 October 2019 / Accepted: 23 February 2020 © The Author(s) 2020
Abstract The implementation of an efficient and sustainable management of the organic fraction of municipal solid wastes (OFMSW) is a topic of intensive discussion in EU countries. Recently, the OFMSW has been investigated as a potential substrate for the production of lactic acid (LA) through fermentation. Nevertheless, none of the reports available in the literature covers all the stages of the conversion process. The present research article is a comprehensive study which includes the upstream, fermentation and downstream for the conversion of OFMSW into LA. Several batches of OFMSW were analysed for the evaluation of sugars released and LA content before the fermentation. Fermentations were performed to study the effect of hydrolysate quality on the LA production using Bacillus coagulans A166. Purification of LA, based on electrodialysis, was carried out after pilot scale fermentation of OFMSW hydrolysates. Results showed that variations in the concentrations of sugars and LA are observed from batch to batch of OFMSW. More specifically, LA can reach high concentrations even before the substrates are hydrolysed, limiting the potential applications of the final product due to low enantiomeric purities. In general, fermentations of the hydrolysate were efficient, with conversion yields of 0.65 g g−1 without the addition of extra nutrients. Downstream is still a challenging stage of the process. A LA recovery of 55% was obtained, with the most significant losses observed during the micro- and nanofiltrations. Overall, a conversion of 10% from OFMSW substrate (dry basis) to LA was achieved. Graphic Abstract
Keywords Lactic acid · Purification · Enzymatic hydrolysis · Bacillus coagulans · Electrodialysis · Pilot scale
Statement of Novelty Although there has been a lot of attention regarding the bioconversion of the organic fraction of municipal solid waste (OFMSW) into energy (biogas), research involving * José Pablo López‑Gómez plopezgomez@atb‑potsdam.de 1
Leibniz Institute for Agricultural Engineering and Bioeconomy, Max‑Eyth‑Allee 100, Potsdam, Germany
the production of lactic acid (LA) from OFMSW has been very limited. Nevertheless, the chemical composition of this material, rich in carbohydrates and proteins, makes it a great substrate for fermentation processes. This study involves the hydrolysis of the OFMSW and the evaluation of how the quality of different batches can impact the final enantiomeric purity of the product, the fermentation stage and also the purification steps. The article includes experimental results from the hydrolysis, fermentation and purification until a final highly pure LA solution was obtained, providing a
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comprehensive overview of the full process, from upstream to purification
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