Proteomic insights into high biohydrogen production by Chlorella sp. KLSc61 under potassium deprivation: upregulation of carbohydrate synthesis proteins
摘要
Microalgae produce hydrogen by utilizing light energy to split water molecules and this produced hydrogen is considered as a promising alternative energy resource. This study investigated the proteomic response of the microalga, Chlorella sp. KLSc61 under an optimal condition for increasing hydrogen production. Chlorella KLSc61 cells were cultured in potassium deprivation medium (TAP-K medium) with an initial pH of 9.0 and added 25 mM ethanol, they were cultivated and exposed to the light intensity of 54 μmol photons m−2 s−1 at 35 °C. By day 7, under this growth condition, Chlorella cells produced a maximum H2 yield of 19,600 ± 0.3 mmol H2 mg−1 chlorophyll, which was 2.5 times greater than that under normal TAP condition. Under an increase of hydrogen production, Chlorella KLSc61 cells were both round- and oval-shaped with an average cell diameter of 10.0 ± 0.5 μm, along with variations of chloroplast distribution within the cytoplasm, whereas Chlorella cells in normal TAP medium showed only round shape with an average cell diameter of 5.0 ± 0.5 μm. Proteins from cells grown under normal and high hydrogen conditions were subjected to proteomic analysis, with the results presented as a cluster heat map of proteomics profiles from five different conditions. A total of 736 protein expression patterns were classified into six different expressed protein groups, which included both up- and down-regulated proteins. Carbohydrate synthesis proteins, including starch synthase, glucose-6-phosphate isomerase, glycerol-3-phosphate dehydrogenase, phosphoglucomutase, and UDP-glucuronate decarboxylase, were abundant during the high H2 production. These findings allow us to take the next step of those protein overexpression into Chlorella KLSc61 cells to enhance in vivo hydrogen production and this strain could be used as a hydrogen production platform.
Graphical Abstract