Optimization of immobilization conditions by conventional and statistical strategies for alkaline lipase production by Pseudomonas aeruginosa mutant cells: scale-up at bench-scale bioreactor level

Suitability of 3 matrices, agarose, sodium alginate, and polyacrylamide, for immobilization of mutant cells of Pseudomonas aeruginosa MTCC 10,055 was investigated. Of these, agarose was proven to be the best as exhibiting maximum enzyme production (4363.4 U/mL), followed by polyacrylamide gel (2172.3 U/mL). Alginate beads were the poorest. The one-variable-at-a-time approach suggested agarose at 2.0%, immobilized bead at 4.0 g blocks/50 mL, and initial cell loading of 0.8 g in the matrix as optimum conditions for maximum lipase production (5982.3 U/mL) after 24 h of incubation. However, response surface methodology studies determined the optimum values of these variables as 1.96%, 4.06 g blocks/50 mL, and 0.81 g of cells in the matrix for maximum lipase production (6354.23 U/mL) within 22.54 h of incubation. The agarose blocks were reusable for 7 cycles without any significant loss in lipase yield. Bench-scale bioreactor level optimization resulted in further enhancement in lipase yield (6815.3 U/mL) at 0.6 vvm aeration and 100 rpm agitation within only 20 h of incubation. Presumably, this is the first attempt for lipase production by immobilized cells of P. aeruginosa at the bioreactor level. The agarose-immobilized mutant cells showed potential candidature for alkaline lipase production at the industrial level.