Efficient Accumulation of Carbonhydrate in Microalgae and It’s Hydrolysis

As efficient photosynthetic microorganism, microalgae can convert solar energy and CO₂ into biomass, such as starch and cellulose, which is the desired feedstock for bioethanol production. In present work, a high carbohydrate content microalgae strain was identified as Scenedesmus raciborskii WZKMT. Simulated flue gas was used as carbon source to study the effect of flue gas on microalgae cell components. Microalgae growth and starch accumulation was inhibited with simulated flue gas, the maximum biomass yield and starch content were 2.14 g/L and 36.23%，while with 7% CO₂, those were 3.25 g/L and 53.16%, respectively. Microalgae cells produced more chlorophyll, protein and lipid when simulated flue gas was used as the carbon source. Fatty acids composition analysis indicated that there was no significant distinction on fatty acids relative content (fatty acid/TFA) between cells aerated using simulated flue gas and 7% CO₂. Liquid hot water was applied in the microalgae pretreatment process to increase the enzyme hydrolysis efficiency. The optimization pretreatment conditions analyzed by response surface methodology were as follows: ratio of liquid to solid 13:1, temperature 147℃, heating time 41 min. Under the conditions, the glucose concentration was 14.223 g/L, the glucose recovery was 89.32%, which was up to 5-fold higher than the one of the sample without LHW pretreatment (17.91%). SEM images of microalgae after LHW pretreatment showed that cells were broken and fibre bundles on cell surface were more exposed.