Value Addition to Cane Molasses, an Industrial Effluent via Sustainable Route

Abstract

Cane molasses is an effluent released from sugar mills during the crystallisation of sugar, and the majority of this effluent is used in the production of ethanol. Gluconic acid (GA) is a valuable chemical whose salts find application in the pharmaceutical industry. Most of the gluconic acid present in India is produced by the electrolytic process, which is energy-intensive. The enzymatic route for producing gluconic acid from glucose present in cane molasses is low-energy consuming and sustainable as the enzymes in an immobilised state are recycled several times without much loss of activity. Invertase, glucose oxidase (GOD) and catalase (CAT) are used for producing gluconic acid. The optimal conditions for maximum yield of GA were determined by conducting several batch experiments using free and immobilised enzymes. The effective ratio for GOD and invertase was 1:2 for both free and immobilisation methods. GA production was maximum at 150 min with GOD of 36 units and 120 min using GOD 36 units, CAT 180 units together respectively. The right mix of alginate and enzyme solution was found to be 8:2 for the successful preparation of enzyme beads during the immobilisation process. 7 U/mL of invertase solution was effective for enhancing the glucose content in the molasses. The study confirmed the reusability of immobilised enzymes for GA production in spite of their reduced yield.