Bioethanol production from waste paper sludge as a fermentation substrate by using xylose fermenting yeast

Present technologies to produce bioethanol largely depend on sugarcane and starch based grains mainly corn, potatoes, etc. On the other hand, use of food grains and sugarcane to produce bioethanol has caused significant stress on food security and food prices. Accordingly, the recent focus has been mainly on lignocellulosic materials as a source for bioethanol. Lignocellulose waste such as waste paper sludge, waste from the pulp and paper industry, has a potential to produce bioethanol. Using paper sludge as a carbon source owns an advantage compared to other lignocelluloses because paper sludge do not requires any pretreatment. Industrial fermentation requires microorganisms which are able to utilize carbon sources such as glucose and xylose, two major sugar present in waste paper sludge, for the production of bioethanol at higher yield. There are numerous yeasts which ferment glucose to bioethanol, but only a few yeasts have been found capable of xylose fermentation, i.e., Candida shehatae, Brettanomyces naardenensis, Brettanomyces bruxellensis, and Scheffersomyces stipitis. This review describes the utilization of paper sludge as a fermentation substrate for bioethanol production by using both xylose and glucose fermenting yeasts.