Assessment of biotechnological potentials of strains isolated from repasso olive pomace in Tunisia

Abstract

The agri-food industry generates significant amounts of byproducts, among them repasso olive pomace (ROP) which are rejected and can constitute a serious environmental problem. Our study aimed to investigate the diversity of microbiota isolated from ROP and screen for their biotechnological potentials. A collection of 102 strains (88 bacteria and 14 fungi) was obtained from a ROP sample. The diversity of the bacterial collection was evaluated by amplification of the internal transcribed spacers between the 16S and the 23S rRNA genes (ITS-PCR) and by 16S rRNA sequencing. Fungal identification was performed by polymerase chain reaction (PCR) amplification of the ITS1–5.8S–ITS2 ribosomal DNA region. The specific enzymatic screening of the detected microorganisms was tested. Partial 16S rRNA gene sequencing performed on 44 isolates showed a high level of identity with known strains. Fungal strains identification showed that they belong to four families: Trichocomaceae, Pleurostomataceae, Mucoraceae, and Bionectriaceae. Our results demonstrated that Gram-positive bacteria were mostly active, particularly for protease, lipase, amylase, cellulase laccase, and for biosurfactant production. From the 88 isolated bacteria, Firmicutes were the most prevalent and microdiverse. Bacillus and Paenibacillus, together with some other Gram-negative bacteria such as Pseudocitrobacter anthropi, and Acinetobacter johnsonii showed significant hydrolytic activities and biosurfactant production. The 14 isolated fungi showed a high capacity of enzyme production. This is the first study in Tunisia describing the microbial diversity in ROP as well as the isolation of Bacillus mojavensis producing lipase. Microorganisms especially fungi present in the repasso olive cake produce diverse hydrolytic enzymes of industrial interest.