Effective valorisation of distillery stillage by integrated production of lactic acid and high quality feed

Abstract

Utilization of distillery stillage from bioethanol production for lactic acid and feed production was studied. The lactic acid fermentation of the stillage was performed by Lactobacillus rhamnosus ATCC 7469 and maximal lactic acid concentration of 50.18 g L-1, yield of 0.90 g g(-1), productivity of 1.48 g L-1 h(-1) and viable cell number of 5 x 10(9) CPU mL(-1) were achieved. Solid residues with biomass remains after lactic acid fermentation were assessed for animal consumption. The content of proteins and ash decreased in the residues after the fermentation, whilst the content of oil and nitrogen free extract was higher when compared to unfermented samples. The digestible (17480.64 kJ kg(-1)) and metabolisable (17389.08 kJ kg(-1)) energies as well as digestibility (966.95 g kg(-1)) of the fermentation residue were very high. The in vitro assessment of L. rhamnosus ATCC 7469 survival in simulated gastric conditions has shown high survival rate (87%). In addition, this bacterium has shown good antimicrobial activity against the most important pathogens and capability to produce exopolysaccharide on different sugars present in animal diet. After effective lactic acid fermentation, the residues could be recommended as a high quality feed for monogastric animals.