Preliminary analysis of the bacterial community in different phases of the olive pomace composting process

Abstract

Olive pomace (OP) is a wet by-product generated in olive oil production, with a high organic load, and high toxicity due to its polyphenol composition. Its production can therefore be an environmental problem for olive oil-producing countries, such as Portugal. Composting may be a way to valorise this by-product, and the microorganisms are the main agents of this aerobic degradation process. The aim of the present study was to study the evolution of the bacterial community along the OP composting process and to isolate and identify bacteria with the purpose of exploring them in the future as composting inoculums. Composting was carried out in four industrial-scale piles with different proportions of OP, nitrogen source, structuring agent, and turnings. Compost samples were collected from the piles at three-time points: initial phase, mesophilic phase, and thermophilic phase. The bacterial isolates, obtained through serial dilutions, were identified by sequencing the 16S rRNA region. The results of composition and diversity, showed significant differences among the composting phases and among piles, suggesting a continuous change of bacterial species throughout the different phases of the OP composting process.