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Optimization and scale-up of a new bacterial bioprocess for lactic acid production

Optically pure lactic acid isomers have been exclusively produced via fermentative routes. Recent developments regarding utilization of different types of raw material as substrates reinforced application of novel principles, technologies and design of sustainable bioprocesses that include hydrolysis of raw material substrate and fermentation of carbohydrates therefrom. The main objectives of our investigation were optimization of bioprocess for D- and/or L-lactic acid production on a laboratory-scale and verification of optimized bioprocess in a proof of concept on a semi-industrial scale. Preliminary studies established laboratory-scale 30 L stirred tank bioreactor as suitable for submerged bioprocesses for the isomers production from different carbohydrates, including soluble starch, by selected bacterial strain. Utilization of starch-type unsoluble substrate (100 g/L) from heterogeneous medium that was tested in the same experimental set-up resulted in reduced bioprocess efficiency, presumably due to unbalanced hydrolysis and fermentation. Therefore, another type of bioreactor - horizontal rotating tubular bioreactor (HRTB) with working volume up to 100 L was used and direct conversion of the starch-type unsoluble substrate to D- and L-lactate by the bacterial strain was monitored.

lactic acid, production, optimization, scale-up

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