High density process to cultivate Lactobacillus plantarum biomass using wheat stillage and sugar beet molasses

Małgorzata Krzywonos*¹ · Thomas Eberhard²

¹Department of Bioprocess Engineering, Wrocław University of Economics, Poland
²Department of Microbiology, Uppsala Genetic Centre, Swedish University of Agricultural Sciences, Sweden

*Corresponding author: malgorzata.krzywonos@ue.wroc.pl

Financial support: This work was financed by the Foundation for Strategic Research (MISTRA) programme for Domestication of micro-organisms (DOM). We thank Su-Lin Leong for critical reading of the manuscript.

Keywords: distillery wastewater, high density fermentation, lactic acid bacteria, Lactobacillus plantarum, sugar beet molasses, wheat stillage.

Background: Owing to the growing interest in biofuels, the concept of a biorefinery where biomass is converted to a variety of useful products is gaining ground. We here present how distillery waste is combined with a by-product from a sugar production, molasses, to form a medium for the growth of Lactobacillus plantarum with yields and biomass densities comparable with conventional industrial media. Such approach enables a cost-effective utilization of the problematic wastewater from ethanol and a by-product from sugar production. It is the first approach that attempts to find low-cost media for the production of Lactobacillus plantarum biomass.
Results: This study suggests that sieved wheat stillage enriched by adding 1.77 g/l yeast extract and 10% molasses (v/v), with NH₄OH used for pH adjustment, may be used as a media for large-scale cultivation of L. plantarum. Such composition of the medium permits a high density of lactic acid bacteria (1.6 x 10¹⁰ cfu/ml) to be achieved.
Conclusions: The use of a fermentation medium consisting of distillery wastewater and molasses to obtain value-added products (such as LAB biomass and lactic acid) is a possible step for classical ethanol production to move towards a biorefinery model production in which all by and waste products are utilized to increase produced values and reduce waste production. This enables a cost-effective utilization of the problematic wastewater from ethanol and sugar production.