The Indian Institute of Technology, Guwahati, researchers have developed an ultrasound-assisted fermentation method to produce a safe sugar substitute called xylitol from sugarcane waste.

The method overcomes limitations and time delays associated with conventional fermentation, the premier institute said on Tuesday. The IIT research team was led by Prof V.S. Moholkar and included Dr Belachew Zegale Tizazu and Dr Kuldeep Roy, who co-authored the research papers.

They are all from the department of chemical engineering, IIT Guwahati. “This research was published in two peer-reviewed journals Bioresource Technology (https://doi.org/10.1016/j.biortech.2018.07.141) and Ultrasonics Sonochemistry https://doi.org/10.1016/j.ultsonch.2018.06.014),” the institute said.Highlighting the importance of this research, Prof.

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

“The researchers used only 1.5 hours of ultrasonication during the fermentation, which means that not much ultrasound power was consumed in the process. Thus, xylitol production from sugarcane bagasse (the waste fibrous material produced after extracting juice from sugarcane, as the raw material) using ultrasonic fermentation is a potential opportunity for forward integration of sugarcane industries in India,” he said.

Xylitol, a sugar alcohol derived from natural products, has potential anti-diabetic and anti-obesogenic effects, is a mild prebiotic and protects teeth against caries.While the IIT Guwahati team’s findings are exciting, Moholkar said 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 (radio-frequency) amplifiers, which remains a major technical challenge,” he said.

Sharing details, the IIT said xylitol is industrially produced by a chemical reaction in which wood-derived 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 per cent of the xylose is converted to xylitol and the method requires extensive separation and purification steps, all of which translate to high price for the consumer.Since fermentation, like the conversion of milk into curd, for example, takes many hours, it poses a major hurdle in using these processes on commercial scales but the IIT team has found ways to overcome these problems.

Ultrasound is sound that has a frequency higher than the human ear can hear. When a solution containing microbial cells is subjected to low-intensity ultrasonic waves, microbial cells eat, digest and excrete faster.“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 number translates to 170g of xylitol per kilogram of bagasse. The yield could be further increased to 0.66g/gram of xylose and the fermentation time reduced to 15 hours by immobilising the yeast in polyurethane foam,” the institute said.