Abstract
Glycolipids had received increasing attention because of their uses in various industries like cosmetics, pharmaceuticals, food and machinery manufacture. Microalgae were competitive organisms to accumulate metabolic substance. However, using microalgae to produce glycolipid was rare at present. In this study, glycolipid content of Chlorella pyrenoidosa and Synechococcus sp. under different nitrate and hydrophosphate levels were investigated. The highest glycolipid contents of 24.61% for C. pyrenoidosa and 15.37% for Synechococcus sp. were obtained at nitrate absence, which were 17.19% for C. pyrenoidosa and 10.99% for Synechococcus sp. at 0.01 and 0 g L−1 hydrophosphate, respectively. Glycolipid productivities of two microalgae could reach at more than 10.59 mg L−1 d−1. Nitrate absence induced at least 8.5% increase in MGDG, DGDG and SQDG, while hydrophosphate absence resulted in over 21.2% increase in DGDG and over 48.4% increase in SQDG and more than 22.2% decrease in MGDG in two microalgae. Simultaneous nitrate and hydrophosphate limitation could make further improvement of glycolipid accumulation, which was more than 25% for C. pyrenoidosa and 21% for Synechococcus sp. These results suggest that nitrogen and phosphorus limitation or starvation should be an efficient way to improve microalgal glycolipid accumulation.
Highlights
Glycolipid is a kind of a complex carbohydrate made of sugar and fat by covalently bound, it can be divided into two categories: sphingoglycolipid and glyceroglycolipid
Przytocka-Jusiak et al.[24] reported that rich nitrogen concentration caused an inhibition of cell division for C. vulgaris. These results suggested that C. pyrenoidosa be able to grow in nitrogen limitation or starvation conditions, while Synechococcus sp. be more stringent with nitrogen source C. pyrenoidosa
Benning et al.[32] and Ohta et al.[2] mentioned that phosphate concentration in growth medium strongly influences DGDG and SQDG content in cyanobacteria. These results suggest that microalgae should be similar to higher plants that increase the content of DGDG and SQDG when grown on phosphorus limitation or starvation conditions
Summary
Glycolipid is a kind of a complex carbohydrate made of sugar and fat by covalently bound, it can be divided into two categories: sphingoglycolipid and glyceroglycolipid. The growth and metabolic substance accumulation of microalgae can be affected greatly by environmental factors. Altering the environmental factors of microalgae cell growth can be an effective way to obtain metabolic substance. Liang et al.[14] studied the effects of phosphorus on lipid accumulation in Chlorella sp., found that phosphorus limitation could increase glycolipid content to 10%. The content of three main kinds of glycolipid MGDG, DGDG and SQDG in microalgae could be affected by nitrogen and phosphorus concentration[15,16,17]. The glycolipid contents in these studies were not that high, it still could be further improved. According to our previous research[18], Chlorella pyrenoidosa shows advantages like fast growth and high lipid content. They were chosen in the present research to evaluate the glycolipid accumulation of microalgae under different nitrate and hydrophosphate levels, with a focus on the changes of three glycolipid contents, and optimize a suitable condition for glycolipid accumulation
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