‘Xylitol’: IIT-Guwahati develops method to produce sugar substitute from bagasse

The substitute – ‘Xylitol’ – is produced from bagasse (the residue left after crushing sugarcane) and the process overcomes operational limitations of chemical methods of synthesis and time delays associated with conventional fermentation

In a major breakthrough, researchers at the Indian Institute of Technology in Guwahati (IIT-G) have developed an ultrasound-assisted fermentation method to produce a safe substitute for sugar which has potential anti-diabetic and anti-obesogenic effects.

The academic complex of IIT-Guwahati. (File Photo)

The substitute – ‘Xylitol’ – is produced from bagasse (the residue left after crushing sugarcane) and the process overcomes operational limitations of chemical methods of synthesis and time delays associated with conventional fermentation, the IIT-G media cell said on Tuesday.

“With increasing awareness of the adverse effects of white sugar (sucrose), not only for patients with diabetes, but also for general health, there has been a rise in the consumption of safe alternative sweeteners,” an official release said.

“Xylitol, a sugar alcohol derived from natural products, has potential anti-diabetic and anti-obesogenic effects, is a mild pre-biotic and protects teeth against caries,” it added.

The research team, led by professor VS Moholkar of the institute’s chemical engineering department, included Dr Belachew Zegale Tizazu and Dr Kuldeep Roy who co-authored the research papers. The research has been published in two peer-reviewed journals – Bioresource Technology and Ultrasonics Sonochemistry.

“The use of ultrasound during the fermentation process not only reduced the time of fermentation to 15 hours (against almost 48 hours in the conventional processes), but also increased the product yield by almost 20%,” Moholkar said.

“Researchers used only 1.5 hours of ultrasonication during fermentation. Thus, xylitol production from bagasse using ultrasonic fermentation is a potential opportunity for forward integration of sugarcane industries in India,” he added.

Xylitol is industrially produced by a chemical reaction in which D-xylose, a costly chemical, is treated with nickel catalyst at very high temperatures and pressures that makes the process highly energy consuming.

Only 8-15% of the xylose is converted to xylitol and the method requires extensive separation and purification steps, all of which translate to a high price for the consumer.

As fermentation is a slow process that takes several hours, it poses a major hurdle in using these processes on commercial scales. To overcome both issues of excess energy consumption and long duration taken for fermentation, IIT-G researchers used two approaches.

First, they used sugarcane bagasse, the waste fibrous material produced after extracting juice from sugarcane, as the raw material. This overcomes the cost limitations of current xylitol synthesis methods and provides a method to upcycle a waste product.

Secondly, they used a new type of fermentation process wherein the microbe-induced synthesis of xylitol is hastened by the application of ultrasound waves.

“Under normal conditions, the fermentation of the xylose to xylitol would take 48 hours, but the team hastened the process by subjecting the mixture to ultrasound waves,” the IIT-G release said.

“Without ultrasound, only 0.53g xylitol was produced per gram of xylose, but on subjecting the process to ultrasound, the yield was 0.61g/gram of xylose. This translates to 170 g of xylitol per kilogram of bagasse,” it added.

The yield can be increased to 0.66g/gram of xylose and the fermentation time reduced to 15 hours by immobilising the yeast in polyurethane foam.

“The present research has been carried out on laboratory scale. Commercial implementation of sonic fermentation requires the design of high-power sources of ultrasound for large-scale fermenters, which in turn requires large-scale transducers and RF amplifiers, which remains a major technical challenge,” Moholkar said.