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Background Microalgal starch is regarded as a promising alternative to crop-based starch for biorefinery such as the production of biofuels and bio-based chemicals. The single or separate use of inorganic carbon source, e.g., CO 2 and NaHCO 3 , caused aberrant pH, which restricts the biomass and starch production. The present study applied an in situ CO 2 –NaHCO 3 system to regulate photosynthetic biomass and starch production along with starch quality in a marine green microalga Tetraselmis subcordiformis under nitrogen-depletion (−N) and nitrogen-limitation (±N) conditions. Results The CO 2 (2%)–NaHCO 3 (1 g L −1 ) system stabilized the pH at 7.7 in the −N cultivation, under which the optimal biomass and starch accumulation were achieved. The biomass and starch productivity under −N were improved by 2.1-fold and 1.7-fold, respectively, with 1 g L −1 NaHCO 3 addition compared with the one without NaHCO 3 addition. NaHCO 3 addition alleviated the high-dCO 2 inhibition caused by the single CO 2 aeration, and provided sufficient effective carbon source HCO 3 − for the maintenance of adequate photosynthetic efficiency and increase in photoprotection to facilitate the biomass and starch production. The amylose content was also increased by 44% under this CO 2 –bicarbonate system compared to the single use of CO 2 . The highest starch productivity of 0.73 g L −1 day −1 under −N cultivation and highest starch concentration of 4.14 g L −1 under ±N cultivation were both achieved with the addition of 1 g L −1 NaHCO 3 . These levels were comparable to or exceeded the current achievements reported in studies. The addition of 5 g L −1 NaHCO 3 under ±N cultivation led to a production of high-amylose starch (59.3% of total starch), which could be used as a source of functional food. Conclusions The in situ CO 2 –NaHCO 3 system significantly improved the biomass and starch production in T. subcordiformis . It could also regulate the starch quality with varied relative amylose content under different cultivation modes for diverse downstream applications that could promote the economic feasibility of microalgal starch-based biofuel production. Adoption of this system in T. subcordiformis would faci...

Vapor–liquid equilibrium (VLE) at P = 50.0 and 100.0 kPa have been determined for the binary system (ZE-2-methyl-2-butenenitrile + 2-methyl-3-butenenitrile). To analyze the binary data, the vapor pressures of ZE-2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile were determined, and the experimental values were correlated using an Antoine-type equation. The vapor pressures predicted by the Antoine equation had average relative deviations of 1.964% and 0.907% from the experimental values for ZE-2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile, respectively. Thermodynamic consistency tests were performed for all of the VLE data using the point test, area test, and direct test, and all of the data passed the three tests. The VLE binary data were all calculated from activity coefficients correlated using the Wilson and NRTL models. The model parameters were obtained, and all of the models represent the experimental values quite well.

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