Comparison Between a Newly Isolated Yeast Strain and Lalvin EC-1118 for Enhanced Ethanol Yield from Sugarcane Molasses Employing Batch and Modified Fed-Batch Fermentation

This study was conducted for the purpose to enhance ethanol yield from a newly isolated yeast strain employing batch and modified fed batch fermentation strategies. Saccharomyces cerevisiae strain MZ-4 exhibiting 15% (v/v) ethanol tolerance was isolated and compared with commercial yeast Lalvin EC-1118 for maximum fermentation efficiency. During batch fermentation employing strain MZ-4, maximum ethanol yield was determined as 11.1% (v/v) with 69.3% fermentation efficiency in the presence of 25% (w/v) sugar concentration, 10% inoculum, 0.1% (w/v) ammonium chloride and potassium ferrocyanide at 33 degrees C and pH 5.0, in 72 h. Strain Lalvin EC-1118 exhibited 10.9% (v/v) ethanol yield with fermentation efficiency of 68.1%, after the addition of 0.1% (w/v) diammonium hydrogen phosphate and 0.4% (w/v) potassium ferrocyanide under its optimal conditions i.e., pH 4.5, inoculum size of 7.5% and incubation at 30 degrees C for 72 h. However, during fed batch fermentation, strain Lalvin EC-1118 and MZ-4 exhibited 13.9% and 13.5% (v/v) ethanol with fermentation efficiency of 81.1% and 83.2% using 1.090 specific gravity and feeding interval of 12 and 24 h, respectively. Hence, it is concluded that strain Lalvin EC-1118 demonstrated better ethanol yield; however, comparatively high fermentation efficiency was observed in case of a newly isolated strain MZ-4, employing a modified method of fed-batch fermentation.