Enzymatic Pretreatment of Plant Cells for Oil Extraction

Oil from oilseeds can be extracted by mechanical extraction (pressing), aqueous extraction, or by extraction with organic solvents. Although solvent extraction is the most efficient method, organic solvents are a potential hazard to the life and health for workers as well as to the environment, when solvent vapours are released and act as air pollutant with a high ozone-forming potential. Pressing is safer, environmentally friendly, and it preserves valuable natural components in the resulting oils. The problems associated with pressing are the high energy consumption and the lower yield of oil extraction, because the applied mechanical force does not completely destroy the structural cell components storing the oil. In seed cells, the oil is contained in the form of lipid bodies (oleosomes) that are surrounded by a phospholipid monolayer with a protein layer on the surface. These lipid bodies are further protected by the seed cell walls consisting mainly of poly-saccharides such as pectins, hemicelluloses and cellulose, but also of glycoproteins. The use of hydrolases to degrade these barriers is a promising pretreatment strategy to support mechanical extraction and improve the oil yield. It is advisable to use a combination of enzymes with different activities when considering the multicompartment and multicomponent structure of oilseed cells. This article gives an overview of the microstructure and composition of oilseed cells, reviews enzymes capable of destroying oil containing cell compartments, and summarizes the main parameters of enzymatic treatment procedures, such as the composition of the enzyme cocktail, the amount of enzyme and water used, temperature, pH, and the duration of the treatment. Finally, it analyzes the efficiency of proteolytic, cellulolytic and pectolytic enzyme pretreatment to increase the yield of mechanically extracted oil from various types of vegetable raw materials with the main focus on oilseeds.