Biomass and oil production of green Microalgae scenedesmus sp. using different nutrients and growth
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2012 |
Mikrodumbliai dėl greito augimo, gebėjimo kaupti aliejų, fiksuoti anglies dioksidą, taip pat dėl galimybės valyti nuotekas, tampa vis įdomesniu ir patrauklesniu objektu, kai jų biomasė panaudojama biodegalams gaminti. Siekiant nustatyti žaliadumblio Scenedesmus sp. optimalias augimo ir aliejaus kaupimo sąlygas, tirtos skirtingos auginimo sąlygos, taip pat ir autotrofinis auginimas, taikant azoto stygiaus metodą ir miksotrofinį auginimą, naudojant skystas atliekas ir techninį glicerolį. Nustatyta, kad, taikant azoto stygiaus metodą, miksotrofinėmis auginimo sąlygomis žaliadumblis augo geriau, o aliejaus kaupimas padidėjo dešimteriopai, palyginti su įprastinėmis autotrofinėmis auginimo sąlygomis. Didžiausia biomasės ir aliejaus koncentracija pasiekta auginant mikrodumblius terpėje su techniniu gliceroliu. Ištyrus mikrodumblio biomasės elementinę sudėtį, nustatyta, kad naudojant glicerolį, kai žaliadumblis auginamas, padidėja C:N santykis iki optimalaus biodujų gamybai. Gauti tyrimų rezultatai parodė, kad skystų atliekų ir techninio glicerolio naudojimas gali efektyviai pakoreguoti mikrodumblio biomasės sudėtį. Tuomet ji tampa tinkama biodegalams gaminti.
Biofuel is mostly produced from oleaginous crops, such as rapeseed, sunflower, soybean. The search for new technologies and new feedstock for biofuel production is becoming an increasingly important issue for researchers. Special attention is turned to the raw materials which do not compete with food industry. Microalgae ability, due to their rapid growth, to accumulate oil, to treat wastewater and waste, seems to be a very attractive new object to be used for biofuel production. In this study we have investigated different microalgae growth conditions, including both autotrophic cultivation by means of nitrogen deprivation mode and mixotrophic cultivation by applying liquid waste and technical glycerol for determining the best growth and oil production conditions. It is found that applying nitrogen deprivation mode and mixotrophic growth conditions, microalgae Scenedesmus sp. have grown faster and accumulation of their oil has increased 10.88 times compared to that under autotrophic growth conditions using the usual amount of nitrogen. The highest biomass concentration (2.16 gL-1) is obtained by adding 5 gL-1 glycerol into the growth medium, whereas the highest oil concentration (15.12 %) is reached when using 10 gL-1 technical glycerol. In addition, the elemental composition of microalgae biomass has been analyzed. Results indicate that the usage of glycerol for cultivation of microalgae increases C : N ratio to optimum (19.25) for biogas production, and algae biomass could be used for this biofuel production without adding any other co-substratum. The results of our study show that addition of cheap products: liquid waste and technical glycerol can effectively adjust the composition of microalgae biomass, making it more suitable for biofuel production.