Temperature and Salinity Effect on Tolerance and Lipid Accumulation in Halamphora coffeaeformis: an Approach for Outdoor Bioenergy Cultures

Abstract

Biodiesel production from the microalgal oil of the estuarine diatom Halamphora coffeaeformis has proven to be technically viable. However, a fuller understanding of the environmental factors that regulate its tolerance and neutral lipid accumulation is required for improved mass cultivation in seawater-based outdoor raceway ponds. Meteorological conditions and evaporation processes can significantly influence factors such as the salt levels, water temperature and nutrient and light availability in these systems. Laboratory experiments with H. coffeaeformis growing in f/2 medium were therefore carried out in order to evaluate the effect of temperature and salinity on its growth and tolerance ranges and the effect of salinity on its total lipid and lipid fraction content and fatty acid methyl ester profile. Results indicate that the temperature and salinity ranges of the species were 5 °C to 30 °C and 5‰ to 95‰, respectively. The optimum temperature was between 20 and 25 °C, and the optimum salinity was 20‰. Neutral lipid accumulation increased in cells adapted at 45‰ with respect to those growing at 20‰. Total lipid composition at 45 ‰ was characterized by 85.5% neutral lipids, 2.5% phospholipids and a high percentage of C16.1 (36.4% of total fatty acids). These properties are important for an adequate quality of biodiesel. The eurytolerant behaviour of H. coffeaeformis and the effect of salinity stress on its growth and neutral lipid accumulation are demonstrated. The findings indicate the beneficial attributes of this strain for the development and feasibility of seawater-based outdoor raceway ponds for biodiesel production.

Review of phenotypic response of diatoms to salinization with biotechnological relevance

“…In addition, they can increase enzymatic activity of, e.g., superoxide dismutase, peroxiredoxin, and thioredoxin to detoxify ROS (Rijstenbil, 2003;Krell et al, 2008;Roncarati et al, 2008). Since all of the mentioned acclimation strategies need extra energy, diatoms can vary the adenosine levels of the cells which support the cellular energy charge (Prestegard et al, 2014) or accumulate lipids in order to store energy and carbon (Cheng et al, 2014;Ishika et al, 2018;Navarro et al, 2021).…”

“…In the last decades, we witness the significant development of biotechnology. Diatoms seem to be a promising source (Seckbach & Gordon, 2019) as their special morphological features and intracellular processes may provide several unexplored potential for further industrial application especially in connection with salinization (Ishika et al, 2018;Navarro et al, 2021). However, there are many unanswered questions in this area.…”

Removal of the Basic and Diazo Dyes from Aqueous Solution by the Frustules of Halamphora cf. salinicola (Bacillariophyta)

“…Halamphora spp. has gained attention due to its ability to accumulate a high amount of triglycerides (TAG) for biodiesel production [ 4 , 5 , 6 , 7 ], fatty acids for the aquaculture [ 8 , 9 ] and cosmetics industries [ 10 ], as well as fucoxanthin and chrysolaminarin with antioxidant, anticancer, and immunomodulatory capacities for pharmaceutical purposes [ 11 , 12 ]. Thus, Halamphora strains can be cultivated on an industrial scale for biodiesel, while wastes from lipid extraction may be purified and clean biosilica can be used in different applications.…”