| Abstract [eng] |
The aim of research was to investigate the usability of agro-industrial by-products, such as wheat bran and wheat straw in the production of L-lactic acid via fermentation applying by newly isolated lactic acid bacteria strains (LAB). Agro-industrial by-products were fermented with LAB belonging to Lactobacillus and Pediococcus genera. Before fermentation enzymatic treatment of by-products was carried out using carbohydrases. An enzymatic test K-DLATE 07/14 (Megazyme Int. Ireland, Wicklow, Ireland) was used for lactic acid and D/L-lactates determination. The influence of magnesium, calcium and sodium salts on enzymatic hydrolysis efficiency was evaluated. The addition of 50 mg/L of CaCl2, 100 mg/L of MgSO4·7H2O in straw medium increased enzymatic hydrolysis efficiency, whereas the addition of NaCl in range 50-175 mg/L decreased cellulase activity. Lactobacillus delbrueckii subsp. bulgaricus strains produced the highest amount of L-lactic acid in the wheat straw. Lactobacillus delbrueckii subsp. bulgaricus MI - 94,4 g/kg. In wheat bran medium Lactobacillus sanfranciscensis MW15 produced the highest amount of L-lactic acid - 108,6 g/kg. Furthermore, after microbial fermentation the total phenolic content and DPPH radical scavenging activity of fermented wheat straw and wheat bran were determined spectrophotometrically. In wheat straw and wheat bran medium highest antioxidant activity was observed with L. delbrueckii subsp. bulgaricus DSM 20081 and L. delbrueckii subsp. bulgaricus MI respectively, 334 mg and 231 mg of (Trolox equivalent per 100g) and highest total phenilic content was observesed using L. delbrueckii subsp. bulgaricus MI - 1187 mg (Gallic acid equivalent per 100g) in wheat straw and with L. sanfranciscensis MW15 - 766 mg (Gallic acid equivalent per 100g) in wheat bran. The results confirm that tested agro-industrial by-products could be used for L-lactic acid production using selected enzymes and lactic acid bacteria strains. |
