| Abstract [eng] |
Chokeberries (Aronia melanocarpa) are a good source of antioxidants. The main use for this plant is the production of juice from the berries. This results in large amounts of pomace, which is usually treated as a by-product ant utilized. However, there are traceable amounts of biologically active compounds in the pomace. According to scientific literature, the use of genus Bacillus for solid state bioprocessing can enrich the by-products of agricultural and industrial by-products. The aim of this project was to evaluate the effects of solid state fermentation using Bacillus megaterium on the processing of chokeberry pomace into higher value bioactive products. Objectives and methods. To optimize the conditions for solid state fermentation of chokeberry pomace by using Bacillus megaterium, by manipulating key factors of the fermentation, i.e. nutrients, pH, effects of rotation and the volume ration between the substrate and bacterial inoculum. After fermentation, to perform ethanolic and aqueous extractions and calculate and compare the effects of the fermentation on the yield of the extracts. Further, to investigate and compare total phenolic compounds abundant in the extracts using Folin-Ciocalteu method. Also, the antioxidant activity of the investigated extracts was assessed and compared with DPPH and ABTS•+ radical binding assays. Furthermore, to determine and compare the total amount of anthocyanins in the extracts using pH differential spectrophotometric method and to assess the composition of anthocyanins using high-performance liquid chromatography-mass spectrometry (HPLC-MS) method. And at the end of the project, based on the obtained results, to design the recommended principal technological scheme for the experimental model used during the study. Results. The methods for the optimization of the conditions for solid state fermentation of chokeberry pomace using Bacillus megaterium have shown that the microflora is most sensitive to nutrients and pH, compared to other investigated factors. Studies with the effects of rotation and substrate-inoculum volume ratios did not show significant changes in bacterial growth. In addition, solid state fermentation increased the yield of aqueous, but not ethanolic, extracts of the fermented chokeberry pomace. The total phenolic compounds after fermentation significantly increased in aqueous extracts. Antioxidant activity studies have shown that the antioxidant capacity of ethanolic extracts increases after the fermentation and has a significantly higher radical binding potential than the aqueous extracts. The determination of total amount of anthocyanins in ethanolic extracts revealed that solid state fermentation reduced the anthocyanin content in the extracts of chokeberry pomace to an almost undetectable level. This was also confirmed by HPLC-MS that resulted in evidence, that no anthocyanins were detected in the extracts after the fermentation of chokeberry pomace. Conclusions. B.megaterium is a suitable microflora for solid state fermentation of chokeberry pomace. The effectiveness of the fermentation directly depends on the used nutrients and the pH value. Solid state fermentation increases the yield in aqueous, but not ethanolic, extracts of chokeberry pomace. Solid state fermentation increases the total amount of phenolic compounds in the aqueous extracts of chokeberries. In ethanolic extracts, the total phenolic contents is about 5 times higher than that in the aqueous extracts, however, solid state fermentation does not have a significant effect on it. Solid state fermentation increases the antioxidant potential of the ethanolic extracts of chokeberry pomace. The radical binding ability of aqueous extracts were low and solid state fermentation does not have a direct effect on it. Solid state fermentation using B.megaterium reduces the total amount of anthocyanins in chokeberry pomace to an almost undetectable levels. This effect was identified by both pH differential and HPLC-MS assays. |
