Abstract
The utilisation of waste materials and industrial residues became a priority within the bioeconomy concept and the production of biobased chemicals. The aim of this study was to evaluate the feasibility to continuously produce L-lactic acid from different renewable substrates, in a multi-substrate strategy mode. Based on batch experiments observations, Bacillus coagulans A534 strain was able to continuously metabolise acid whey, sugar beet molasses, sugar bread, alfalfa press green juice and tapioca starch. Additionally, reference experiments showed its behaviour in standard medium. Continuous fermentations indicated that the highest productivity was achieved when molasses was employed with a value of 10.34 g·L−1·h−1, while the lactic acid to sugar conversion yield was 0.86 g·g−1. This study demonstrated that LA can be efficiently produced in continuous mode regardless the substrate, which is a huge advantage in comparison to other platform chemicals.
Highlights
The vast majority of lactic acid (LA) produced in the world comes from fermentation processes
Continuous fermentations indicated that the highest productivity was achieved when molasses was employed with a value of 10.34 g·L−1·h−1, while the lactic acid to sugar conversion yield was 0.86 g·g−1
This study demonstrated that LA can be efficiently produced in continuous mode regardless the substrate, which is a huge advantage in comparison to other platform chemicals
Summary
The vast majority of lactic acid (LA) produced in the world comes from fermentation processes. Simple sugars such as glucose and sucrose, obtained mainly from corn, sugarcane, and cassava [1], are used as substrates in LA fermentations. In comparison to processes which use simple sugars, the valorisation of this kind of substrates comprises some extra challenges. They are complex and heterogeneous materials which normally require a pretreatment to make sugars available for microbial growth. Unlike current industrial fermentations in which a single simple sugar is used, fermentation media from alternative substrates usually contain a combination of carbohydrates. In most cases experimental work involved pure sugars that do not replicate the conditions of complex substrates
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