Physiological and Ecological Aspects of Chlorella sorokiniana (Trebouxiophyceae) Under Photoautotrophic and Mixotrophic Conditions

Author(s)

Marchello, Adriano Evandir ^{[1, 2]} ; dos Santos, Alexsandro Claudino ^[1] ; Lombardi, Ana Teresa ^[1] ; Oliveira de Souza, Clovis Wesley ^[3] ; Montanhim, Graziela Cristina ^{[1, 2]}

Affiliation

^[1] Univ Fed Sao Carlos, Dept Bot, Lab Algal Biotechnol, Rodovia Washington Luis 310, Sao Carlos, SP - Brazil

^[2] Univ Fed Sao Carlos, Ctr Biol & Hlth Sci, Rodovia Washington Luis 310, Sao Carlos, SP - Brazil

^[3] Univ Fed Sao Carlos, Dept Morphol & Pathol, Lab Microbiol & Parasitol, Rodovia Washington Luiz 310, Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: MICROBIAL ECOLOGY; v. 76, n. 3, p. 791-800, OCT 2018.
• Web of Science Citations: 1

Abstract

Mixotrophy is a metabolic strategy in which an organism is autotrophic and heterotrophic simultaneously. Considering that the aquatic environment provides several organic sources of carbon, it is probably common for microalgae to perform mixotrophy and not only photoautotrophy, but little is known about microalgae mixotrophy. The present work aimed at investigating the growth, photosynthetic activity, morphology, and biochemical composition of the microalga Chlorella sorokiniana in mixotrophic and photo-mixotrophic conditions, comparing it with photoautotrophy. The results showed pH changes after glucose addition, reaching pH 11.62 in mixotrophic and 10.47 in sequential photo-mixotrophic cultures, which limited the microalgal growth. Highest biomass was obtained in the mixotrophic culture in comparison with the sequential photo-mixotrophic one. Rapid light saturation curves showed that alpha (photosynthetic efficiency, 1.69) and relative electron transport rate (rETR; 565.61) were higher in the mixotrophic cultures, whereas the highest I-k (irradiance saturation, 386.68) was obtained in the photoautotrophic ones. In the sequential photo-mixotrophic cultures, photosynthetic activity varied during glucose consumption, decreasing the maximum quantum yield F-v/F-m after glucose addition, indicating change in metabolism, from photoautotrophy to mixotrophy by the microalga. The results showed that the mixotrophic cultures had higher production of chlorophyll a (6.26 mg mL(-)(1)), cell density (6.62 x 10 7 cell mL(-1)), and lipids (0.06 pg mu m(-)(3)). Sequential photo-mixotrophic cultures showed the highest biovolume (360.5 mu m(-)(3) cell(-1)) and total carbohydrates (0.026 pg mu m(-3)). The protein concentration was 3.2 and 2.4 times higher in photoautotrophy and photo-mixotrophic growth, respectively, than in mixotrophy, but lipids were three times higher under mixotrophy. The biochemical changes we observed indicate that the microalga's plasticity in face of new environmental characteristics, such as the presence of organic carbon, can change the flow of energy through natural ecosystems. (AU)

• FAPESP's process: 14/15894-0 - CO2 fixation by microalgae Chlorophyceae: photosynthesis and biochemical composition under different CO2 concentrations
• Grantee: Ana Teresa Lombardi
• Support Opportunities: Regular Research Grants