Acid Hydrolysis of the wastes of Opuntia Ficus-Indica (L.) Miller in order to produce Bioethanol

Abstract

Opuntia ficus-indica (L.), also referred to as prickly pear or nopal cactus, is commonly utilized in food, medicine, and cosmetics. Typically, cactus pear waste is discarded in nature or fed to cattle. It is composed mainly of water, cellulose, hemicellulose, pectin, extractives, ash, and lignin. Previous studies have indicated that the wastes of cactus pears have a high sugar yield which converts by fermentation into bioethanol. However, this process does not occur naturally; it needs physical pretreatment, acid hydrolysis, enzymatic hydrolysis, and fermentation. Acid hydrolysis pretreatment is necessary because it helps break the interchain linkages in hemicellulose and cellulose. This research aims to determine the optimal conditions for acid hydrolysis of cactus pear wastes using sulfuric acid and hot water to release total reducing sugars. This optimization resulted in 0.121 mol/l of total reducing sugars (TRS) after 20 minutes of reaction time with a 3% sulfuric acid solution at 121°C and a solid-liquid ratio of 1:10. The following were the best conditions for saccharose release: 1,561 mol/l saccharose, 15 minutes of reaction time, 3% sulfuric acid solution, 121°C temperature, and a solid ratio of 1:10