How to combine CO2 abatement and starch production in Chlorella vulgaris

Abstract

Microalgae production has gained attention in recent years as promising systems for CO 2 abatement as well as a source of proteins, pigments, vitamins, lipids, and carbohydrates. Particularly, starch can be used for bioethanol production in a well-established fermentative process. The aim of this work was to maximize and model biomass productivity and CO 2 assimilation in continuous cultures of Chlorella vulgaris. The following culture parameters were studied: dilution rate, pH, temperature, light intensity, and nitrogen supply. The proposed model (r 2 = 0.95) predicted a maximum biomass productivity of 0.7 g L −1 d −1 and CO 2 assimilation of 1.3 g L −1 d −1. The experimental data agreed with these predictions, resulting in a maximum biomass productivity of 0.67 g L −1 d −1 (resulting in a CO 2 assimilation of 1.23 g L −1 d −1). In addition, the starch content was determined, and the results were used as input into a second model, which aimed at predicting starch accumulation during CO 2 abatement processes (r 2 = 0.84). This second model predicted a daily and continuous production of biomass with a maximum starch content of 0.25 g g −1 d −1 (25% dcw), but under different culture conditions than those found for maximizing biomass productivity and CO 2 assimilation. The maximum starch content experimentally determined was 0.2 g g −1 d −1 (20% dcw). Thus, to implement a biological system for CO 2 abatement coupled to starch accumulation, it is necessary to find a compromise between these two processes. Hence, although yield in both processes would be reduced, a simultaneous process for CO 2 mitigation and starch production would be feasible.

Application of an in situ CO2–bicarbonate system under nitrogen depletion to improve photosynthetic biomass and starch production and regulate amylose accumulation in a marine green microalga Tetraselmis subcordiformis

“…However, the single use of NaHCO 3 increased the pH (usually > 10 on the final cultivation day) due to the utilization of HCO 3 − by microalgae that tended to release OH − according to the equilibrium relationship of HCO 3 − + H 2 O ↔ H 2 CO 3 + OH − and H 2 CO 3 ↔ CO 2 + H 2 O, and hence, the biomass production was still limited [16, 17]. Moreover, the starch accumulation could also be influenced by the varied pH environments originated from the different carbon sources used [18, 19]. Therefore, to get an optimized biomass or starch production, suitable supply of carbon source is required to ensure a carbon-abundant environment along with a favorable pH condition.…”

Effect of light intensity, light duration and photoperiods in the performance of an outdoor photobioreactor for urban wastewater treatment

“…It must be highlighted that factors which influence microalgae growth such as solar irradiance [24;39], temperature [54,55], nutrient loading rates [8,53] and culture mixing [17,30] were the same for PBR-A and PBR-B in each experiment, only differing in the artificial lighting regime. In addition, nutrients were maintained in replete conditions (i.e., nitrogen higher than 10 mg N•L -1 and phosphorus above negligible concentration as explained in Pachés et al [62]) during all the Experiments except for 1 and 2A (Figure 2a).…”

“…PBRs were then fed in semi-continuous operation with the same nutrient load, maintaining a hydraulic retention time (HRT) of 8 days. Temperature was in the range of 18-27ºC, which is within the optimum range for green algae Scenedesmus and Chlorella: 15-25ºC [54,55].…”

Unveiling the underlying molecular basis of astaxanthin accumulation in Haematococcus through integrative metabolomic-transcriptomic analysis

“…The methodology described in García-Cubero et al (2018) was used to determine starch content from 5 mg lyophilized samples in 1 mL of chloroform:methanol solution (2:1 v/v).…”