Coproduction of lipids and extracellular polysaccharides from the novel green alga Parachlorella sp. BX1.5 depending on cultivation conditions

Abstract

A novel strain of microalga Parachlorella sp. BX1.5 was isolated and its unique properties of producing lipids and extracellular polysaccharides (EPS) characterized. The cells could extracellularly produce a large amount of acidic EPS, when cultured in nitrogen-deficient BG110 medium (BG11–N) with 2 % CO2-air supply. The main component of intracellularly accumulated lipids was triacylglycerol (TAG), depending on the different cultivation conditions of BG11, BG11–N, BG11–P (phosphate depleted), and BG11–N–P (nitrogen and phosphate depleted). Fatty-methyl-esters (FAMEs), methyl-esterification of total lipids, consisted of abundant saturated C16 and unsaturated C18 fatty acids under the culture conditions. Cell spot assays on BG11 plates revealed the resistance of cells to pH 2–11, high temperatures of 50–70 °C, ultraviolet irradiation, and drought, under different culture conditions, thereby suggesting the biological significance of lipid and EPS accumulation. The prospects of BX1.5 as a dual producer has also been discussed for biorefineries.

Co‐production of microbial lipids with valuable chemicals

“…Exopolysaccharide (EPS) is a kind of extracellular and high‐molecular‐weight polymer, which can be used as an water‐retention reagent and an additive in the food / medical industries 47 . The oleaginous yeast Sporidiobolus pararoseus JD‐2 could co‐produce 41.6 g/L of lipids and 13.1 g/L of EPS in a fed‐batch fermentation from glucose 48 .…”

“…has been reported to be a promising producer for lipid (44.9%) and EPS (1.46 g/L) co‐production 50 . Exopolysaccharide is a sticky layer that wraps the somatic cells closely and protects them from the toxic environment, so a harsh fermentation environment, for example with nutrient depletion or high osmotic pressure, may certainly stimulate EPS production 47 . The co‐production of lipids and EPS might be used for both environment remediation and waste substrate recycling.…”

“…46 Exopolysaccharide (EPS) is a kind of extracellular and high-molecular-weight polymer, which can be used as an water-retention reagent and an additive in the food / medical industries. 47 The oleaginous yeast Sporidiobolus pararoseus JD-2 could co-produce 41.6 g/L of lipids and 13.1 g/L of EPS in a fed-batch fermentation from glucose. 48 The marine diatom Phaeodactylum tricornutum has the capability to accumulate 42.5% of lipids and 57.6 mg/L EPS in nitrogen limitation fermentation.…”

“…50 Exopolysaccharide is a sticky layer that wraps the somatic cells closely and protects them from the toxic environment, so a harsh fermentation environment, for example with nutrient depletion or high osmotic pressure, may certainly stimulate EPS production. 47 The co-production of lipids and EPS might be used for both environment remediation and waste substrate recycling. For example, Cloacibacterium normanense NK6 could produce 22.4 g/L of EPS and 28% content of lipids by using crude glycerol and sludge as substrates.…”

A review on prospective production of biofuel from microalgae

“…The growth expectation of algae is very simple and affordable i.e. sufficient light, naturally available dissolved nutrients and CO 2 [ 37 , 38 ]. Unialgal growth without contamination of other eukaryotic or prokaryotic organisms and axenic culture (bacteria free) is challenging.…”