Microencapsulation of recombinant Saccharomyces cerevisiae cells with invertase activity in liquid‐core alginate capsules

As a means of integrating cell growth and immobilization, recombinant Saccharomyces cerevisiae cells with invertase activity were immobilized in liquid‐core alginate capsules and cultured to a high density. S. cerevisiae cells of SEY 2102 (MAT α ura 3–52 leu 2–3, 112 his 4–519) harboring plasmid pRB58 with the SUC 2 gene coding for invertase were grown to 83 g/L of liquid‐core volume inside the capsule on a dry weight basis. The cloned invertase was expressed well in the immobilized cells with slightly higher activity than the free cells in a batch culture. Invertase in the immobilized cells showed slightly more improved thermal stability than in the free cells. Storage in a Na‐acetate buffer at 4°C and 10°C for 1 month resulted in 7% and 8% loss in activity, respectively. The sucrose hydrolysis reaction was stably maintained for 25 repeated batches for 7 days at 30°C. Continuous hydrolysis of 0.3 M sucrose was carried out in a packed bed reactor with a conversion of more than 90% at a maximum productivity of 55.5 g glucose/L per hour for 7 days. In a continuous stirred tank reactor, the maximum productivity of 80.8 g glucose/L per hour was achieved at a conversion of 59.1% using 1.0 M sucrose solution, and 0.5 M sucrose solution was hydrolyzed for 1 week with a 95% conversion at a productivity of 48.8 g/L per hour. © 1996 John Wiley & Sons, Inc.