A mathematical model of intracellular behavior of microalgae for predicting growth and intracellular components syntheses under nutrient‐replete and ‐deplete conditions

Abstract

Microalgae is a promising biomass source for renewable fuels and chemicals production. To describe microalgal behavior and improve their cultivation, various kinetic models have been proposed. However, previous works have focused on biomass formation and lipids production only, even though carbohydrates and proteins are also important products, not only for understanding the metabolic behavior of microalgae but also for enhancing the economic viability through value-added side products. In this study, a new mathematical model is proposed to explain core biological mechanisms of growth and macromolecules syntheses based on the central metabolism of carbon and nitrogen. In the model, microalgal growth is separated as hyperplasia and hypertrophy, to describe the cell growth more precisely under nutrient-replete and -deplete conditions. Sensitivity analysis performed using the model indicates that cell state (e.g., cell death rate) has a strong effect on the lipid production explaining the difficulty of reproducing a microalgae culture experiment.

Growth performance and nutrient removal of a Chlorella vulgaris-Rhizobium sp. co-culture during mixotrophic feed-batch cultivation in synthetic wastewater

“…Switching to HRT 3 the lipid content slightly decreased from 8.1% to 6.6 %, while the protein content increased (from 25.2% to 26.3%), similarly to what was observed by Lee and co-workers, when cultivating a microalgal consortium under semi-continuous operation at 3-day HRT in secondary effluent wastewater (reduced lipid content, but higher biomass productivity compared to a 6-day HRT) [53]. The reduction in lipid concentration could be therefore related to a sufficient nutrient supply under the lowest HRT tested, which is known to prevent the accumulation of storage compounds in the algal biomass [54], overcoming the stimulatory effect of bacteria. 17…”

The assimilation of glycerol into lipid acyl chains and associated carbon backbones of Nannochloropsis salina varies under nitrogen replete and deplete conditions

“…The glycerol going into central carbon metabolism via G3P can be converted to glyceraldehyde‐3‐phosphate (GAP) and dihydroxyacetone phosphate (DHAP) (intermediates of the Calvin–Benson cycle) and can enter the Embden–Meyerhof–Parnas (EMP) pathway as one of the intermediates of glycolysis. The lower glycolysis pathway will sequentially breakdown GAP to form acetyl‐CoA (the precursor for fatty acid biosynthesis) and/or can enter in TCA cycle to provide carbon skeletons for amino acids synthesis (Huang et al, 2015; Ryu et al, 2018). Additionally, the G3P can also be assimilated in the upper glycolysis pathway (gluconeogenesis) to store carbon reserves as carbohydrates (Villanova et al, 2017).…”

“…This indicates that intact glycerol molecules were in fact directly esterified to fatty acids/polar head groups. The presence of singly and doubly labeled lipid-bound glycerol species CoA (the precursor for fatty acid biosynthesis) and/or can enter in TCA cycle to provide carbon skeletons for amino acids synthesis (Huang et al, 2015;Ryu et al, 2018). Additionally, the G3P can also be assimilated in the upper glycolysis pathway (gluconeogenesis) to store carbon reserves as carbohydrates (Villanova et al, 2017).…”

Evaluation of PV performance prediction model in tropical environment in Senegal

“…Author(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License parameters of PV cells is available (Azqhandi et al, 2017;Campanelli and Hamadani, 2018;Ryu et al, 2018). A number of past works have described different simplified methods of estimating the long-term average performance of photovoltaic systems or system components (Nishioka et al, 2003) (Jones and Underwood, 2002;Evans, 1981).…”