Microbial composting of fruit tree wastes through controlled submerged fermentation

The ecological valorising of organic compounds represented by many derived wastes from fruit processing through the controlled microbial composting was established as the main aim of research experiments 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 140-230 h, the fermented composts, containing the microbial biomass developed through biochemical transforming of marc into natural fertilisers, were produced.