The maximum glucose consumption rate of 13.45 g/L/h was obtained with 300 g/L, which was 1.78, 1.52, and 1.18 times those of 100, 200, and 500 g/L, respectively.
The glycolytic enzymes had maximum activity at alkaline pH values and the maximum glucose consumption was observed between pH 8 and 11 (Figure 5).
Kinetic parameters describing glucose consumption are ( V_{hbox{max} G} ) maximum glucose uptake rate, ( K_{mG} ) saturation constant for glucose uptake, ( C_{E0} ) initial concentration of ethanol, ( K_{EG} ) ethanol inhibition constant for glucose uptake, ( C_{A0} ) initial concentration of acetate, and ( K_{AG} ) acetate inhibition constant for glucose uptake.
As a result, the maximum specific glucose consumption rate (2.71 ± 0.04 g/g DW/h) was about 2.5 times faster than the maximum specific D-xylose consumption rate (1.10 ± 0.00 g/g DW/h), which was reached just after glucose was completely exhausted (Table 1).
The maximum of glucose consumption rate indicates high metabolic activity and probably high biomass increase.
However, the maximum specific glucose consumption rate was slightly higher in the parent strain (1.4-fold) (Table 1).
The maxima of the TA, AOH and AME production rates were calculated for 100 h, 175 h and 215 h of cultivation, respectively, whereas the maximum of the glucose consumption rate was determined for 125 h of cultivation.
Evolution in repetitive batch cultures influenced the maximum specific growth rate, specific glucose consumption rate and ethanol productivity whereas, evolution in chemostat cultures influenced specific conversion rates of inhibitors.
This combination leads to the optimum glucose consumption rate and maximum product formation.
Whereas, maximum lipid accumulation, biomass production and glucose consumption values in multi-response optimization were observed 28.9%, 1271.2 mg L−1 and 89.2%, respectively at optimum level of 16.8 mM NaNO3, 300.9 μM K2HPO4 and 2.6% (w/v) glucose.
Based on the glucose consumption measurements, the maximum production of lactic acid occurred between pH 8 and 9 β-galactosidase and lactate dehydrogenase, the two enzymes that are upstream and downstream respectively, in the glycolytic pathway, had optimum activity at alkaline pH values (Figure 6) [21], [21].
