Novel biological conversions: Development of value -added products from food -processing wastes and bioremediation of polymeric dyes
Food-processing by-products such as apple and cranberry processing wastes and fishery wastes were used in this study as the substrates for microbial bioconversion of value-added products such as beneficial fungal inoculants, for agriculture applications, food-grade enzymes for food processing applications, and phytochemicals for functional foods and food preservation.
Three Trichoderma species, a Penicillium strain, and Rhizopus oligosporus were selected for producing beneficial bioinoculants from apple and cranberry processing wastes through solid-state fermentation. The effects of CaCO3, water, and NH 4NO3 on the growth of selected fungi were investigated, and the medium was optimized for maximum growth of each microorganism on apple and cranberry pomace. Fish protein hydrolysates were good supplementary nitrogen sources to fruit-processing wastes for microbial growth. The glucosamine content of fermented mixture was a good indicator of fungal biomass measurement during such heterogeneous solid-state fermentation.
Both Trichoderma inoculants; and their water extracts produced from apple pomace significantly enhanced seed germination and seedling vigor in pea (Pisum sativum). They not only stimulated the seed germination and plant growth, but also increased the content of phytochemicals such as phenolics in seedlings. These results showed the potential of such bioinoculants in agricultural, food and pharmaceutical applications.
Cranberry pomace was also a good substrate for bioconversion of food-grade enzymes such as β-glucosidase and phytochemicals such as phenolic acids by solid-state fermentation with a mushroom fungus Lentinus edodes . The enzyme had a low pH optimum and high stability at high temperature, thus has a potential applications in wine and juice processing for aroma and flavor enhancement.
In bioremediation studies, a novel polymeric dye-degrading Penicillium species was isolated and identified. The isolate was able to aerobically decolorize both Poly R-478 and Poly S-119 in liquid systems. The decolorization involved initial mycelial adsorption of dye compounds followed by biodegradation through microbial metabolism, and it may be affected by medium constituents.
Phytoremediation of polymeric dyes was also investigated with the use of several dye-tolerant oregano, thyme and rosemary clonal lines. As a result of natural defense mechanisms of plants, the total phenolics of most clonal lines decreased in response to polymeric dyes, whereas peroxidase activity increased. Stereomicroscopic observations revealed that the polymeric dyes were sequestered within the growing axis of the roots. Such polymeric dye-tolerant plants could be further targeted for developing pollutant tolerant rhizospheres that could accelerate microbial degradation of polymeric dyes and related aromatic compounds.