Surfactant assisted production of ricinoleic acid using cross-linked and entrapped porcine pancreas lipase

Abstract

This work studied hydrolysis of castor oil to ricinoleic acid, catalyzed by immobilized porcine pancreas lipase (PPL) and impact of surfactant on its augmentation. In immobilization of lipase through entrapment in calcium alginate beads, concentration of calcium chloride (CaCl2) was the most significant factor. Optimum conditions for immobilization were, 1.3 M CaCl2 and 12% (w/v) sodium alginate. On cross-linking with glutaraldehyde after entrapment in calcium alginate bead, PPL led to 2.7-fold higher hydrolysis compared to only entrapped PPL. Most suitable surfactant and speed of agitation were Span 80 and 300 rpm, respectively, in enhancing ricinoleic acid production involving cross-linked and entrapped PPL. Central composite design and subsequent optimization with response surface methodology (RSM) found optimum production (recovery) as 21.2% (in 3 h and 25 °C) under the optimum set of process conditions like 9.96 mg lipase/ml, pH of 8.8, 0.014 M Span 80, 2.98% (v/v) glutaraldehyde, 1.3 M CaCl2 and 12% (w/v) sodium alginate. Each of concentration of lipase, pH, surfactant (Span 80) concentration and glutaraldehyde concentration was found to be highly significant. Interactions between any two of these four variables remained insignificant. On varying temperature keeping other variables at their optima, maximum recovery for free lipase (31.29% in 3 h) was obtained at 35 °C; whereas, for immobilized lipase, recovery was maximum (26.27% in 3 h) at 45 °C. Immobilized lipase acted much better than free lipase at higher temperatures.