Bacillus coagulans as microbial cell factory for L-lactic acid production from agricultural and forestry waste

Research Project, 2016 – 2018

This is an international collaborative project that aims at establishing the thermophilic bacterium Bacillus coagulans as a microbial cell factory for the production of L-lactic acid from lignocellulosic biomass.

Lactic acid is being increasingly used as a renewable bio-based product to replace petroleum-based plastics. Moreover, it is a useful additive in foods, pharmaceuticals, and cosmetics. One of the goals in biotechnological development is to pave the way to the utilization of microbes for waste bioconversion. In this context, the gram-positive bacterium Bacillus coagulans has been shown to be promising for industrial production of L-lactic acid. However, this currently relies on the utilization of carbohydrate feedstocks competing with food industries. Our Italian collaborators from the Molecular Biology and Biochemistry of Extremophiles laboratories (Department of Biology, University of Naples Federico II) have isolated a thermophilic strain of B. coagulans that is able to grow at 55°C and pH 5.5-6.0, using carboxymethyl-cellulose or filter paper as its sole carbon source. These growth conditions are close to the optimal range of activity of fungal cellulases, which are employed nowadays for the saccharification of lignocellulosic biomass. The use of this kind of biomass as carbon and energy source for B. coagulans fermentation has great potential. Therefore, we are testing the ability of this newly isolated strain to produce L-lactic acid from such biomasses in a simultaneous saccharification and fermentation (SSF) configuration. The demonstrated ability of this strain to depolymerize cellulose would allow reducing the concentration of heterologous enzymes required for the biomass conversion to monomeric sugars, which are then fermented to L-lactic acid. Moreover, we aim at setting up a consolidated bioprocess (CBP), in which this strain will be tested for the simultaneous production of depolymerizing enzymes and the fermentation of sugars to L-lactic acid, thus greatly reducing the costs of the entire production process.