BIOTECHNOLOGICAL PRODUCING OF NATURAL FERTILIZERS THROUGH MICROBIAL COMPOSTING OF FRUIT WASTES

In Romania, to protect the natural environment and save its biodiversity there is an urgent need to solve a lot of serious damages caused by the pollution effects induced through discharging of fruit wastes into natural aquatic ecosystems (streams, rivers, lakes), in huge amounts, after their fermentation and alcohol extraction made in private horticultural farms. The efficient valorising of such organic compounds, represented by many derived wastes from fruit processing, through biotechnological means was establish to be the main aim of certain research experiments whose results are presented in this paper. There were carried out laboratory works to test the optimal needs of bacterial and fungal pure cultures to grow inside different marc made of apple, cherry and plum wastes (chemical composition, temperature, pH, oxygen/carbon dioxide concentration). In this respect, there were used pure bacterial cultures of Bacillus genus as well as the fungal ones belonging to species of Pleurotus for microbial transformation of different fruit wastes. The biotechnology of microbial composting was applied by using a laboratory-scale bioreactor of 15 L working volume. The submerged fermentations of different fruit wastes were set up for the following parameters: constant temperature, 23°C; agitation speed, 80-100 rev. min-1; pH level, 5.7?6.0 units; dissolved oxygen tension within the range of 30-70%. After a period of submerged fermentation lasting between 140- 230 h, there was produced fermented composts containing the microbial biomass that was developed through biochemical transforming of marc into natural fertilizers. By using pure cultures of bacterial and fungal species, in strict hygienic conditions and permanent control of microbial processes induced for fruit waste composting it was ensured the optimum performance of tested biotechnological proceedings to increase the biochemical transformations of marc as compounds with a high content in proteins and other organic compounds that are very useful as natural fertilizers of agricultural crops.