The potential for lactic acid production in brown juice

Student thesis: Master Thesis and HD Thesis

  • Martine Holmberg Olesen
4. term, Sustainable Biotechnology, Master (Master Programme)
In this thesis the potential for utilizing brown juice as a fermentation media for lactic acid production was examined. Green juice was initially utilized as fermentation media because it contains a Carbon source. Both juices are both characterized chemically, determining VFA, TS, VS, free sugars, Total Kjeldahl Nitrogen and soluble sugars. Bacteria were isolated from both the green juice and the brown juice. These bacteria were screened for lactic acid production together with a positive control L. salivarius. During this screening several fermentation conditions were also tested. The conditions chosen after completion were sterile aerobic conditions. Following the screening two isolated bacteria and L. salivarius, were tested for lactic acid production at different pH. The highest concentration, 21.5 g/L, was observed at pH 6.5 which is the value the future fermentation media were adjusted to. Finally, different Carbon sources (glucose, xylose and press cake) were tested in the brown juice yielding very little lactic acid production, but there was butyrate production. It was hypothesized that the switch to nonsterile conditions, were the primary reason for this. It was ultimately discovered that while a concentration of 21.5 g/L lactic acid could be obtained by fermentation in brown juice, there was a much bigger potential for butyrate production. The highest butyrate concentration obtained was 45 g/L.
Publication date10 Jun 2016
Number of pages73
ID: 235054505