Bioconversion of Olive Pomace by Submerged Cultivation of Streptomyces sp. S1M3I

Abstract

Olive pomace is an abundant low-cost agro-industrial residue in Mediterranean countries, including Algeria. The aim of the present study was the biotreatment of olive pomace in submerged culture with Streptomyces sp. S1M3I in order to produce lignocellulolytic enzymes and to upgrade the nutritional value of olive pomace for incorporating in the livestock feed. The selected strain was cultured on submerged medium based olive pomace at 40 °C for 30 days, and subsequently, the lignocellulolytic activities, the viability of the microorganism and the chemical composition of the resulting substrate, were determined. Streptomyces sp. S1M3I exhibited activities, of 11.2 ± 0.12 U/mL for xylanase, 1.44 ± 0.02 U/mL for cellulase and 1.21 × 10−2 U/mL for laccase. A significant (p < 0.05) decrease in the hemicellulose, cellulose and lignin content was registered. Maximum of viability (2.71 × 109 cfu/mL) of Streptomyces sp. S1M3I was registered on the 7th day, followed by a decline caused by polyphenol release into the culture medium (4.37 ± 0.04%). However, the total phenolic content in dry matter (DM) during the incubation period remained significantly (p < 0.05) stable. An increase in crude protein content with 34.18% and a decrease in total lipid content with 82.23% were registered. The quantities of 98.03 ± 4.85 and 123 ± 3.6 mg/g DM have been obtained, for reducing sugar and total sugar, respectively, after 30 days of incubation. Olive pomace can be valorized by submerged culture of Actinobacteria strains; this can be an interesting alternative for biotechnological processes.