While carrying out a lignocellulosic lactic acid fermentation process with the addition of calcium carbonate, it was that found that the control (uninoculated) runs containing calcium carbonate resulted in a low colormetric reading using the Megazyme D-glucose enzymatic analysis kit (gopod) in comparison with control experiments omitting calcium carbonate. Those containing calcium carbonate observed glucose of approximately 15g/L after 72 hrs while experiments without calcium carbonate showed glucose of 50-60g/L. In addition, in some instances the solution resulted in a precipitation when gopod was added for analysis in experiments containing calcium carbonate while those without it did not cause precipitation. The calcium carbonate (30g/L) was added to neutralize the pH when lactic acid was produced so that the pH of the medium remained within for the microorganisms optimal production and survival. With this in mind, controls (uninoculated) were set up in conjunction with the experiments to determine glucose utilization. To corroborate this low concentration, another Megazyme D-glucose hexokinase kit and the DNS method was used and found similar results.

Is there a specific reason for this result? Is there any other protocol available to address the issue as well?