Conversion of Thin Stillage Compounds Using Endemic Bacteria Augmented with Lactobacillus panis PM1B

A consortium of organisms, endemic in wheat-based thin stillage (W-TS), obtained from a commercial ethanol production converts glycerol to 1,3-propanediol (1,3-PD) and lactic acid to acetic acid. We sought to improve conditions for 1,3-PD and acetic acid production to be used in future studies of industrial isolation of these compounds from two-stage fermentation. Occasionally, stillage fermentation proceeded slowly, but an inoculum of Lactobacillus panis PM1B augmented both fermentation rate and extent. Fermentation rate and product yield were enhanced by adjusting pH to 5 daily and adding glucose and glycerol (molar ratio 0.1:1), freeze-dried W-TS, and vitamins (B₂, B₃, and B₁₂). 1,3-PD and 3-hydroxypropionaldehyde (3-HPA) did not inhibit 1,3-PD production during fermentation. Moreover, agitation did not improve fermentation rate or extent. Corn sugar was a suitable substitute for glucose. Fermentation was performed at both 20 and 150 L with 1,3-PD production of 2% (w/v, 20 g/L) being routinely achieved or exceeded.