Analyzing the Potential of Sugarcane Juice for Bio-ethanol Production

Abstract

Sugarcane (Saccharum sp. hybrid complex) is an important industrial crop as a source of food and bio-energy. Its juice can act as a cheaper renewable substrate for bio-ethanol production because it contains free sugars like sucrose or monosaccharides (especially, glucose) that can be directly converted into ethanol via fermentation with the help of microorganisms. The present study reports on bio-ethanol production potential of 22 different sugarcane varieties/clones (early and mid-late) that were initially screened for cane yield and components traits, physiological and juice quality traits. Among 22 clones/varieties, six varieties viz, CoPb 95, CoPb 92, Co 0118, CoPb 93, CoJ 88, and Co 0238, were identified for good bio-ethanol production potential on the basis of leaf area (cm²), fresh weight (kg), Brix (%), extraction (%) and fiber (%) cane. These varieties were further evaluated for other biochemical traits and bio-ethanol production potential under laboratory scale and scale-up studies using yeast strain (Saccharomyces cerevisiae MK 680910). Two varieties CoPb 92 (early) and CoJ 88 (mid-late) having higher initial sugars and ethanol content under laboratory scale were selected as potential sugarcane varieties for scale-up studies. Study at 5 L scale reported that CoPb 92 variety exhibiting initial Brix (20.97%), total sugars (20.05 g/100 mL), and reducing sugars (0.567 g/100 mL), yielded 12.40 (%v/v) initial ethanol content with fermentation efficiency of 96.21 (%) and ethanol yield 0.50 (g/g) in early group. After double distillation of the fermented wort, the ethanol content of 78.46% (v/v) was achieved with ethanol recovery of 0.329 L. Similarly, variety CoJ 88 reporting initial Brix (20.24%), total sugars (19.88 g/100 mL), and reducing sugars (0.814 g/100 mL juice) yielded initial ethanol content of 11.68 (%v/v) with fermentation efficiency of 94.49 (%) and ethanol yield of 0.47 (g/g) in mid-late group. Recovery of 0.301 L ethanol was obtained after double distillation with ethanol content of 75.45 (%v/v). The sustainability of economy/ revenue of sugar industry relies on either reduction in the production cost of sugar or to divert sugar industry toward energy and power generation. Therefore, a cultivar intended for the production of ethanol ought to possess elevated levels of total sugars or percentage of commercial cane sugar, in conjunction with a substantial cane yield. The information generated in the present study can be added as a basic input to scale-up technical process toward enhancing the production of bio-fuel in sugar industries by switching over from sole sugar production to ethanol production, depending on the situations (sugar deficit/sugar surplus) in the market.