MICROENCAPSULATION OF RECOMBINANT SACCHAROMYCES-CEREVISIAE CELLS WITHINVERTASE ACTIVITY IN LIQUID-CORE ALGINATE CAPSULES

As a means of integrating cell growth and immobilization, recombinant Saccharomyces cerevisiae cells with invertase activity were immobilize d in liquid-core alginate capsules and cultured to a high density. S. cerevisiae cells of SEY 2102 (MAT alpha ura3-52 leu2-3, 112 his4-519) harboring plasmid pRB58 with the SUC2 gene coding for invertase were g rown to 83 g/L of liquid-core volume inside the capsule on a dry weigh t basis. The cloned invertase was expressed well in the immobilized ce lls with slightly higher activity than the free cells in a batch cultu re. Invertase in the immobilized cells showed slightly more improved t hermal stability than in the free cells. Storage in a Na-acetate buffe r at 4 degrees C and 10 degrees C for 1 month resulted in 7% and 8% lo ss in activity, respectively. The sucrose hydrolysis reaction was stab ly maintained for 25 repeated batches for 7 days at 30 degrees C. Cont inuous hydrolysis of 0.3 M sucrose was carried out in a packed bed rea ctor with a conversion of more than 90% at a maximum productivity of 5 5.5 g glucose/L per hour for 7 days. In a continuous stirred tank reac tor, the maximum productivity of 80.8 g glucose/L per hour was achieve d at a conversion of 59.1% using 1.0 M sucrose solution, and 0.5 M suc rose solution was hydrolyzed for 1 week with a 95% conversion at a pro ductivity of 48.8 g/L per hour. (C) 1996 John Wiley & Sons, Inc.