Bioethanol Production Using Starch Extracted from Microalga Stigeoclonium sp., Kutz. BUM11007 Cultivated in Domestic Wastewater

Microalgae are considered one of the viable feedstocks having potential to replace agricultural products for bioethanol production. The culture costs of microalgae remain the major hurdle in using them to produce bioethanol. This study focuses upon cultivation of a freshwater branched microalga Stigeoclonium sp., Kütz. BUM11007 in domestic wastewater and use the biomass for bioethanol production by Saccharomyces cerevisiae. Initially the microalga Stigeoclonium sp., was tested for their efficiency to remove the nutrients from different wastewater. When the organism was allowed to grow in wastewater they almost use all the available nutrients from the medium within 14 day. Among the various culture setups established, maximum growth (2.38±0.34 g LG1 dry cell weight) was observed from the setup composed of a wastewater (WW1) with 50% strength of Chu10 medium. The carbohydrates and starch contents of the cell were almost similar among the different culture setups. The algal biomass was harvested and tested for their usefulness in bioethanol production. The algal biomass was acid treated to dissolve the complex sugars. The sugar extract was used as the fermentation medium for bioethanol production with Saccharomyces cerevisiae. After 24 h of anaerobic fermentation, the yield was quantified as 0.195 g ethanol/g of microalgal biomass. The result proves the possibility of developing integrated process for bioethanol production with microalgal biomass cultivated from wastewater.