Vol. 1, Issue 1, Part A (2019)

The objective of this study was to determine and compare the cell yield of Escherichia coli grown in minimal medium containing different concentrations of glucose (0.025%, 0.050% and 0.075%) and lactose (0.025%, 0.050% and 0.075%). Determination of the cell yield was done by oven drying the harvested cells to obtain the dry weight and analysis of the residual sugar in the liquid medium by phenol-sulfuric acid method. Highest initial concentration of glucose (596.667 ppm) and lactose (563.333 ppm) was recorded in minimal medium supplemented with 0.075% of the respective sugar. E. coli grown in 0.050% glucose (354.167 ppm) and 0.025% lactose (266.667 ppm) had the highest substrate consumed. Highest cell dry weight (µg/mL) and cell yield (µg/mL) was obtained in 0.075% glucose and 0.075% lactose. Comparing the two sugars, still, glucose had the highest cell yield (glucose 0.050% = 217.368 µg/mL and lactose 0.050% = 195.146 µg/mL; glucose 0.075% = 572.923 µg/ml and lactose 0.075% = 295.146 µg/ml). Highest Y^substrate was also recorded in highest sugar concentration (glucose 0.075% = 2.331; lactose 0.075% = 1.638). No statistical significance was observed when Y^substrate of different sugar concentrations were compared.