Estudo fisiológico de Chlorella sorokiniana e Chlorolobion lunulatum sob diferentes condições de cultivos em escala laboratorial e ampliada (200 L)

Abstract

The cultivation of microalgae is growing worldwide and has gained relevance in recent years. On a larger scale, such cultivation is costly and, to make it feasible, finding effective strategies to increase biomolecules and biomass in the production system can be a solution. The microalgae chosen for this study were Chlorella sorokiniana and Chlorolobion lunulatum, two Chlorophyta species that support semi-controlled environmental conditions. This study was divided into 3 chapters, starting with laboratory experiments, and ending with culture scale expansion to 200 L. On Chapter one we focused on a low-cost nutrient medium for biomass production. Chapter 2 reports on a biochemical manipulation procedure to increase biomolecules in the biomass through exposure of the Chlorophyta to NaCl and, chapter 3 focused on 200 L cultures of C. lunulatum in a green house, under semi-controlled conditions. For the 200 L culture, the mixotrophic metabolism was considered to overcome some limitations in biomass production. Finally, with the results of the 200 L cultures, a techno-economic study was developed. As the low-cost nutrient medium, a modified hydroponic solution was tested to replace the BG11 synthetic medium. These results showed that despite having reduced costs, the hydroponic solution did not support greater cell density and did not lead to the accumulation of biomolecules compared to the control. The biochemical manipulation with NaCl, concentrations that would not negatively affect the growth rate, but only stimulate the accumulation of biomolecules (2 g L-1 NaCl) were sought. These results showed that C. sorokiniana produced 5 times more total carotenoids (0.59 mg L-1) than C. lunulatum, but C. lunulatum ~2 times more lipids (~30% of dry biomass). However, there was no influence of NaCl on lipid production. Finally, in the 200 L cultivation, which was carried out only with C. lunulatum, the treatment with sodium acetate as a source of organic carbon resulted in a 32% increase in the production of dry biomass (2.7 g L-1) compared to the control. Although the addition of sodium acetate increased the operating cost by 4.8% and reduced the biomass production cost of by 21% the production system, the amount of biomass produced would still need to be greater for a favorable production cost. This research highlights the potential of the microalgae C. lunulatum for biotechnological applications and the importance of optimizing cultivation conditions to increase the production of biomass and specific biomolecules.