Bioreaction Engineering Leading to Efficient Synthesis of L-Glyceraldehyd-3-Phosphate

Enantiopure L-glyceraldehyde-3-phosphate (L-GAP) is a useful building block in natural biological and synthetic processes. A biocatalytic process using glycerol kinase from Cellulomonas sp. (EC 2.7.1.30) catalyzed phosphorylation of L-glyceraldehyde (L-GA) by ATP was used for the synthesis of L-GAP. L-GAP has a half-life of 6.86 h under reaction conditions. The activity this enzyme depends on the Mg²⁺ to ATP molar ratio showing maximum activity at the optimum molar ratio of 0.7. A kinetic model was developed and validated showing a 2-D correlation of 99.9% between experimental and numerical data matrices. The enzyme exhibits inhibition by ADP, AMP, methylglyoxal and Ca²⁺, but not by L-GAP and inorganic orthophosphate. Moreover, equal amount of Ca2+ exerts a different degree of inhibition relative to the activity without the addition of Ca²⁺ depending on the Mg²⁺ to ATP molar ratio. If the Mg²⁺ to ATP molar ratio is set to be at the optimum value or less, inorganic hexametaphosphate (PPi6) suppresses the enzyme activity; otherwise PPi6 enhances the enzyme activity. Based on reaction engineering parameters such as conversion, selectivity and specific productivity, evaluation of different reactor types reveals that batchwise operation via stirred-tank reactor is the most efficient process for the synthesis of L-GAP.