The range of values was established in order to assess the influence of each parameter in final resveratrol production and cell physiology. The influence of the conditions tested on resveratrol yield and productivity, cell growth and viability and plasmid segregational stability can be seen on Table 2. As expected, if the concentration of precursor added was 0 mM (assay 11), the production is

approximately null. It was also observed that low concentrations of resveratrol were generally associated with higher concentrations of precursor, as a concentration of 12 mM of p-coumaric acid allowed the attainment of a resveratrol productivity click here of 2.98 mg/gh−1 (assay 5) while a concentration of 4 mM allowed an almost two-fold increase of resveratrol productivity to 5.09 mg/gh−1 (assay 3), with the same correlation being obtained in terms of resveratrol

volumetric yields. It can also be observed that p-coumaric acid seemed to have a detrimental effect Epacadostat on cellular growth, as higher concentrations of p-coumaric acid added resulted in lower OD600 values (assays 4, 5, 8, 9, and 15) when compared to assays without or with lower concentrations of p-coumaric acid (assays 2, 3, 6, 7, and 11). The influence of temperature can be seen by the resveratrol yield analysis when observing the assays results for 25, 31, and 37 °C with the other variables constant (assay 1, 13 and 25, respectively). It was observed that for the lowest (25 °C) and highest (37 °C) tested temperatures, resveratrol

production was low, with the best results, both in terms of volumetric yield and productivity being achieved for assays at 28 and 31 °C (assays 2–16), thus corroborating the results obtained for this parameter in the screening assays. However, at 25 °C (assay 1, Table 2), E. coli did not produce high amounts of resveratrol as 25 °C is not within the E. coli optimal growth range, which can result in slower transport processes and growth [25], and consequently lower resveratrol production. Although 37 °C is the temperature Tryptophan synthase closer to the optimum E. coli growth temperature [25] this temperature may lead to trans-resveratrol degradation [22], since it is an easily degradable compound [21], which resulted in lower production levels. Regarding the pH, a pH around 6.5–7.0 seemed to be an optimal value to produce resveratrol, since the production tripled from 32.53 μg/mL, at a pH of 6.0 (assay 10), to 100.59 μg/mL, at a pH of 7.0 (assay 13) and then decreased again to 26.32 μg/mL (assay 16), at a pH of 8.0. The same trend was also observed for resveratrol specific values that almost tripled from 1.37 (pH 6.0) to 3.44 (pH 7.0) and then decreased again to 1.24 (pH 8.0). This pH influence on resveratrol production could be related with the optimal pH for E. coli growth as seen in the screening assays. In these assays, the OD600 at the time of induction had a slight impact on final production.