Glucose addition‐induced changes in the growth and chemical compositions of a freshwater microalga Chlorella kessleri

Abstract

BACKGROUND In recent years, mixotrophic culture of algal cells has been gaining increasing interest, largely because it offers an efficient means of commercial production of lipids and other value‐added products. In this work, the impacts of glucose addition on the biomass production, chemical composition and fatty acid profiles of Chlorella kessleri were investigated to exploit the relationships between extra organic carbon and changes in the distribution of chemical compositions in algal cells. RESULTS Results showed that C. kessleri grew fast in the mixotrophic cultures with a maximum algal biomass and specific growth rate of 4.46 g L−1 and 1.27 day−1, respectively. Glucose in the cultures was absorbed and utilized effectively by this alga, whose uptake efficiencies ranged from 88.2% to 98.3%, but it had a negative impact on the synthesis of photosynthetic pigments. Additionally, the culture's pH and chemical composition, including pigments, carbohydrate, protein and lipids, in this alga varied with the change of glucose concentrations in the cultures. The fatty acid profiles of this alga indicated that its biomass could be used as live feeds in aquaculture or a good‐quality feedstock for biodiesel production. CONCLUSIONS These results suggested that adding an extra organic carbon source (glucose) to a photoautotrophic culture was a potentially effective way to improve the performance in mixotrophically culture of microalgae, for example in terms of higher biomass and lipid production. © 2018 Society of Chemical Industry

Insights into the physiology of Chlorella vulgaris cultivated in sweet sorghum bagasse hydrolysate for sustainable algal biomass and lipid production

“…However, in our study, even though glucose was mixotrophically consumed within 6 days, the chlorophyll a and chlorophyll b contents continued to decrease possibly due to nitrogen depletion. Our findings are in line with previous studies, where a decrease in photosynthetic pigments was recorded under mixotrophy 29,47,48 . Interestingly, carotenoid content remained unchanged in the cells at 1.5-1.8 mg/g DCW (Fig.…”

“…Such an increase in pH was due to the fixation of CO 2 by algae causing generation of OHions that are neutralized by H + ions in the media 29,30 . However, when the culture reached early stationary phase with negligible growth and nitrate uptake, the pH dropped due to accumulation of H + ions from the release of organic acids by the cells into the culture media.…”

“…5d). Glucose is known to partially block the transformation of coproporphyrin III, a precursor of chlorophyll a 29 . Actually, after sugar depletion under mixotrophic conditions, algae can switch back to photosynthesis by enhancing pigment synthesis 46 .…”

Mixotrophic cultivation of Scenedesmus dimorphus in sugarcane bagasse hydrolysate

“…For biomass raised mixotrophically in medium SCBH‐I, chlorophyll a and b were 2.94 ± 0.12 and 1.19 ± 0.28 μg/mg DW, respectively and which are 91 and 89% lower than the respective figures obtained for photoautotrophic cultivation (Figure ). According to the previous report, utilization of external carbon source under mixotrophic conditions affect negatively on production of photosynthetic pigments . In another study, glucose inhibited carbon dioxide fixation by 10 folds and resulted in decreased photosynthetic pigment contents under mixotrophic conditions .…”

New Insights into Xanthophylls and Lipidomic Profile Changes Induced by Glucose Supplementation in the Marine Diatom Nitzschia laevis

“…In addition, as shown in the TEM images ( Figure 2 G), the thylakoid membranes were less abundant and less compact in MC cells, although the volume of the chloroplasts had no visible defect. Some researchers have reported that glucose has negative impacts on photosynthesis by reducing CO 2 apparent affinity and chlorophyll contents or repressing the expression of proteins, such as chlorophyll-binding proteins evolved in PSII, the PSII reaction center protein D1, and Rubisco in the Calvin cycle [ 26 , 27 , 28 ].…”