Guwahati, Aug 23: A research team from the Indian Institute of Technology-Guwahati (IIT-G) has developed an ultrasound-assisted fermentation method to produce a safe sugar substitute called ‘xylitol’ from the fibrous residue post extraction of juice from sugarcane.
An official statement from the institute said on Tuesday that the new method overcomes the operational limitations of chemical methods of synthesis and the time delays associated with conventional fermentation.
Of late, consumption of safe alternative sweeteners has increased with growing awareness of the adverse effects of white sugar (sucrose), not only for patients with diabetes but also for general health.
A sugar alcohol derived from natural products, xylitol has potential anti-diabetic and anti-obesogenic effects, is a mild prebiotic and protects teeth against caries.
Led by Prof. V.S. Moholkar from the department of chemical engineering, IIT-G, the research team also comprised Belachew Zegale Tizazu and Kuldeep Roy, who co-authored the research papers.
The research was published in two peer-reviewed journals, Bioresource Technology and Ultrasonics Sonochemistry.
Highlighting the importance of the 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 percent.”
The researchers used only 1.5 hours of ultrasonication during the fermentation, which means that not much ultrasound power was consumed in the process.
Xylitol is industrially produced by a chemical reaction in which wood-derived D-xylose, a costly chemical, is treated with a nickel catalyst at very high temperature and pressure that makes the process highly energy consuming.
Only eight to 15 percent of xylose is converted to xylitol and the method requires extensive separation and purification steps, all of which translate to high price for the consumer.
Fermentation is a biochemical process that is attractive to tackle these issues. In fermentation, one substance is converted to another using various types of microorganisms such as bacteria and yeast.
However, fermentation processes are slow – the conversion of milk into curd, for example, takes many hours, which poses a major hurdle in using these processes on commercial scales.
The IIT Guwahati researchers used two approaches to overcome such problems: First, they used sugarcane bagasse, the residue left after crushing 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.
The researchers first hydrolysed the hemicellulose in bagasse into carbon (pentose) sugar such as xylose and arabinose. For this, they chopped the bagasse into small pieces and treated them with dilute acid.
The sugar solution was then concentrated and a form of yeast called Candida tropicalis was added to this to bring about fermentation.
Under normal conditions, fermentation of xylose to xylitol takes 48 hours. But the team hastened the process by subjecting the mixture to ultrasound waves.