Valorization of winery and oil mill wastes by microbial technologies

•Winery and olive oil wastes contamination problems are reviewed.•By-products obtained from winery and olive oil industries are described.•The microbial processes are a feasible option for treatment of residues.•Biofuels, additives, polymers and enzymes can be produced by these technologies.•Future trends regarding winery and olive oil waste management have been considered.

Agro-food industrial wastes represent a serious environmental problem in producing countries. In addition to the traditional irrigation with wastewaters, application of solids to the land, and the extraction of valuable compounds for the pharmaceutical, cosmetics and food industries, a microbiological approach is also available. In this review, the most promising microbiological processes for the valorization of wine and oil by-products are presented. Recently, there has been an upsurge in the exploitation of the waste materials generated by the wine and olive oil industries. Treatments by physical and chemical methods are generally expensive, and they do not often provide complete solutions. Microbiological processes for the treatment of olive and grape residues have seen worldwide applications, and they are considered to be environmentally friendly, reliable and, in most cases, cost effective. Production of added-value products such as edible mushrooms, biofuels, organic acids, polymers and enzymes appear to be the new frontier in by-products valorization. Our study has been focused in these two major food industries in the Mediterranean area, engaged in wine and olive oil production.