The use of NaCl addition for the improvement of polyhydroxyalkanoate production by Cupriavidus necator.

External stress factors in the form of ionic species or temperature increases have been shown to produce a stress response leading to enhanced PHA production. The effect of five different NaCl concentrations, namely 3.5, 6.5, 9, 12 and 15 g/l NaCl on PHA productivity using Cupriavidus necator has been investigated alongside a control (no added NaCl). A dielectric spectroscopy probe was used to measure PHA accumulation online in conjunction with the chemical offline analysis of PHA. The highest PHA production was obtained with the addition of 9 g/l NaCl, which yielded 30% higher PHA than the control. Increasing the addition of NaCl to 15 g/l was found to inhibit the production of PHA. NaCl addition can therefore be used as a simple, low cost, sustainable, non toxic and non reactive external stress strategy for increasing PHA productivity.