Feasible Novozym 435-Catalyzed Process to Fatty Acid Methyl Ester Production from Waste Frying Oil: Role of Lipase Inhibition

Fatty acid methyl ester (FAME) or biodiesel is a biofuel conventionally produced from edible oil and methanol, using an alkaline catalyst, through a transesterification reaction. As FAME is mostly produced from edible vegetable oils, crop soils are used for its production, increasing deforestation and producing a fuel more expensive than diesel. In addition, between 70 and 80% of the total FAME production costs correspond to the vegetable oils. Therefore, the use of waste lipids such as waste frying oils (WFO), waste fats and soapstock has been proposed as low-cost alternative to feedstock. Non-edible oils such as jatropha, pongamia and rubber seed oil are also economically attractive. In addition, microalgae, bacteria, yeast and fungi with 20% or higher lipid content are oleaginous microorganisms known as single cell oil and have been proposed as feedstock for FAME production. Alternative feedstocks are characterized by their elevated acid value due to the high level of free fatty acid (FFA) content, causing undesirable saponification reactions when an alkaline catalyst is used in the transesterification reaction. The production of soap consumes the conventional catalyst, diminishing FAME production yield and simultaneously preventing the effective separation of the produced FAME from the glycerin phase. These problems could be solved using biological catalysts, such as lipases or whole cell catalysts, avoiding soap production since the FFAs are esterified to FAME. In addition, by-product glycerol can be easily recovered and the purification of FAME is simplified using biological catalysts.