Difference between revisions of "Part:BBa K1675008"

Revision as of 23:03, 27 September 2015

A device used in the synthesis of lactic acid

L-Lactic acid, one of the most important chiral molecules and organic acids, is produced via pyruvate from carbohydrates in diverse microorganisms catalyzed by an NAD-dependent L-lactate dehydrogenase. The LdhA gene is used in the synthesis of lactic acid. This gene encodes an L-lactate dehydrogenase (L-LDH) which converts pyruvate to L-lactate.

To verified the LdhA gene, we constructed our gene into pET28a (Fig.1), and induced its over-expression by IPTG (Isopropyl β-D-1-Thiogalactopyranoside) under 16 ℃ in BL21(DE)3.

Fig.1 The constructed result of LdhA-pET28a

Meanwhile, we put glucose as the substrate of glycolysis (40% glucose solution, add 2ml to 48ml culture solution). After 12 hours fermentation, we measured the pH of the culture fluid. We use the pET28a(BL21(DE3)) as the control. We repeated this process three times and our result is shown in Table.1.

According to the Table.1, we could easily found that there is an obvious difference between experimental group and control. Under the anaerobic condition, L-lactate dehydrogenase, coding by LdhA, acts much better ability than under aerobic condition. However, the final pH value of culture fluid is bigger than pKa of lactic acid. We suppose that the bacteria take advantage of lactic acid, due to the lack of carbon source.

Fig.2 The final fermentation result of the basic regulation system under acidic stress. By calculating the pH change of unit active biomass in unit time, This figure can be drawed.

Fig.3 The growth curve of E.coli with basic regulation circuit under acidic stress.

Fig.4 The final fermentation result of the basic regulation system under alkaline stress. By calculating the pH change of unit active biomass in unit time, This figure can be drawed.

Fig.5 The growth curve of E.coli with basic regulation circuit under alkaline stress.

Sequence and Features