AP-03: Valorization of tomato wastes in a solid stat fermentation for protease production by new Algerian fungal isolates

Abstract

Agro-industrial wastes are of increasing interest due to their potential applications as cheap substrates for production of bioactive compounds. To obtain valuable new products, new microbial strains have been screened from nature. Advantages of fungi producers are as they are Generally Recognized As Safe and produce a wide range of extracellular enzymes.

The aim of this study is to determine the capacity of new fungal isolates to use at different temperatures tomato pomace for protease production. For this, fungal isolates from soil samples of a hydrothermal spring in Algeria were screened for their proteolytic activities by the ability to form clear zones around colonies on milk agar plates. Further morphological identifications were investigated for the selected isolates. They were inoculated on a solid medium based on tomato pomace moistened with distilled water in 250ml shake flasks, then statically incubated at four temperatures 30°C, 35°C, 40°C and 45°C for 96 h. Strains showing high activities were cultivated on tomato pomace moistened by a solution with optimum components of a previous study. Among fifty proteolytic isolates, nine revealed large diameters of halos surrounding their colonies. They were selected to be identified in the following genera: Aspergillus, Trichoderma, Penicillium and Scopulariopsis. Fungi belonging to the Aspergillus genus exhibited the best proteolytic activities using tomato wastes as a sole source of carbon and nitrogen, where the best activity (3840 U) was observed by Aspergillus sp. 6 at 35°C. About 25% of increase in protease activity was reported by Aspergillus sp. 6 when employing the optimum formulation of the humidification solution. From the present work, our results confirm the value of tomato pomace as an alternative cheap substrate in the fermentation media for protease production as given its high protein content. We can also conclude that these microorganisms could be promising source of bioactive compounds