pH and CO sub(2) effects on Coelastrella (Scotiellopsis) rubescens growth and metabolism

• Published in: Russian journal of plant physiology Vol. 63; no. 4; pp. 566 - 574
• Main Authors: Minyuk, G S, Chelebieva, E S, Chubchikova, IN, Dantsyuk, N V, Drobetskaya, I V, Sakhon, E G, Chivkunova, O B, Chekanov, KA, Lobakova, E S, Sidorov, R A, Solovchenko, A E
• Format: Journal Article
• Language: English
• Published: 01.07.2016
• Subjects: Chlorophyceae; Scenedesmaceae; Sphaeropleales
• ISSN: 1021-4437; 1608-3407
• DOI: 10.1134/S1021443716040105

We studied effects of р Н and С О sub(2) enrichment on the physiological condition and biochemical composition of a carotenogenic microalga Coelastrella (Scotiellopsis Vinatzer) rubescens Kaufnerova et Elias (Scenedesmaceae, Sphaeropleales, Chlorophyceae), a promising source of natural astaxanthin. The microalga was grown at a constant pH (5, 6, 7 or 8) maintained by direct С О sub(2) injection. The air-sparged culture served as the control. Cell division rate and size, dry biomass productivity, the rates of nitrogen and phosphorus uptake as well as photosynthetic pigment and total lipid content and fatty acid composition were followed. С . rubescens possessed a narrow-range р Н tolerance (the optimum р Н 6-7). Under these conditions, the highest values of the maximum (1.0-1.1 1/day) and average (0.3-0.35 1/day) specific growth rate, chlorophyll а (4.8-4.9%) and total carotenoid dry weight percentages (1.7-1.8%) were recorded. Cell lipid fatty acid unsaturation index (1.851) and polyunsaturated fatty acid percentage (36-39%) and С 18:3 omega 3/С 18:1 omega 9 ratio (3.8-4.5) were also the highest under these conditions. A decline of р Н to 5 brought about severe stress manifesting itself as a cell division cessation, photosynthetic apparatus reduction, two-fold increase in cell volume, accumulation of dry weight and lipids and a considerable decline in fatty acid unsaturation. Cultivation of С . rubescens without С О sub(2) enrichment resulted in a rapid alkalization of the medium to р Н 9.5-10.5 impairing the physiological condition of the cells. Reasons of the deteriorative effects of suboptimal pH values on the physiological condition of C. rubescens are discussed.