(159x) Lipase Immobilization on Mesoporous Carbon and Evaluation As Catalysts in the Hydrolysis of Waste Oleochemical Streams.

The acid-catalyzed high pressure and temperature hydrolysis of refined vegetable oils and fats is typically used in the manufacture of fatty acids, which in turn are used as basic oleochemical intermediates for a variety of derivatives. This process is highly energy intensive and the severe conditions can drive a variety of undesirable side reactions. Alternatively, enzymatic hydrolysis can be run near to ambient conditions and with a high selectivity, thus reducing capital and energy costs and the associated environmental impacts. Despite of the high conversion, selectivity and benign conditions, the industrial implementation of the enzymatic processes is still challenging owing to the high cost of the enzymes, the lower reaction rates compared with homogeneous catalysts, and the deactivation that can be exacerbated by impurities contained in the feedstock.

In order to improve the enzymatic processes, immobilization techniques have been used to enhance enzymes stability and selectivity, simultaneously facilitating recovery and re-utilization. Besides ultrasound comes as an alternative to the enzymatic process optimization. At the same time, the use of immobilized catalysts can help overcoming the stability issues when processing waste streams as feedstock of the hydrolysis process. This is particularly important because reclaiming and exploitating waste oleochemical streams (e.g. used cooking oil, trap greases, yellow-brown-black fat, crop mill effluents) is paramount to reduce major environmental impacts of the food/feed production chain. Currently there are commercial immobilized lipases, but they are characterized by low yields and slow kinetics in the hydrolysis of refined oils and fats. This occurs partly because the enzymes have been immobilized under microporous and partially hydrophilic materials (e.g. silica, alumina, zeolites).

In this regard, the immobilization of enzymes on mesoporous and hydrophilic supports seems a feasible pathway to enhance their effectiveness in the hydrolysis of waste oleochemical streams. Also, an additional degree of improvement can be obtained by using an intensified ultrasound-assisted process. In this work, immobilized Lipase from Candida Antarctica was prepared by physical adsorption on mesoporous carbons and using crosslinking with glutaraldehyde and polyethylenimine. The obtained structure was characterized by an extended hydrophobic surface, facilitating the lipase interfacial activation, and enhancing the activity. Also, the mesoporous structure enhanced acylglycerides mobility and diffusion of obtained fatty acids through the porous catalyst. Hydrolysis reactions were carried out under ultrasound-assisted conditions at 37 and 80 kHz at 37 ºC using different molar ratios of water to oil ( 9:1, 5:1, 1:1 and 1:3). For comparison purposes, the reaction was carried out also with a commercial lipase (Novozyme® 435). Experiments disclosed 24% higher conversion than commercial lipase and a 70% relative activity remain up to 5 cycles. It was found that the immobilized lipases on the highly hydrophobic mesoporous material had better performance on waste oleochemical hydrolysis than the commercial, in yield and reusability terms. In this regard, enzyme immobilization on mesoporous and hydrophilic supports seems a feasible pathway to enhance their effectiveness in waste oleochemical streams ultrasound-assisted hydrolysis.