Sorbitol from pizza boxes: from Ca’ Foscari a new 'green' patent

Left to right: Giancarmelo Stamilla, Daniele Polidoro, Maurizio Selva e Alvise Perosa

An economically viable and sustainable alternative to traditional methods of converting cellulose into sorbitol has emerged from the laboratories of Ca' Foscari University of Venice.

The process, developed by professors Alvise Perosa and Maurizio Selva with doctoral students Daniele Polidoro and Giancarmelo Stamilla from the Department of Molecular Sciences and Nanosystems, is now a patent pending, and can contribute to the development of a sustainable bio-economy for a number of major industrial sectors, such as pharmaceuticals, food, cosmetics and textiles.

The invention, presented by Giancarmelo Stamilla, won Falling Walls Lab Italy - promoted by the University of Milano-Bicocca in partnership with the Universities of Milan, Bergamo, Pavia, Bocconi University, MUSA scarl, PoliHub, Social Innovation Teams and Netval - and will be presented in November to academic and business experts from 100 countries at the Falling Walls Conference in Berlin.

Giancarmelo Stamilla at the Falling Walls Lab Italy 2023

“Sorbitol is a sugar substitute with a wide range of industrial uses, for example it is a common ingredient in cosmetics and food products,” says Alvise Perosa, professor of Chemistry. “Chemically, sorbitol is a 'building block', a simple molecule that can go into the construction of more complex molecular structures. It is obtained from cellulose, the most widespread polymer in nature and the starting point of sustainable chemistry. Cellulose is extracted from plants and is composed of carbon, oxygen and hydrogen. Treating cellulose with acid produces glucose, commonly known as sugar. Through chemical or biological processes, glucose can in turn be transformed into sorbitol”.

To date
, converting cellulose to sorbitol is unsustainable and costly in terms of time, money and resources. The process takes place in two steps that require two separate facilities. In the first step, cellulose is treated with an acid hydrolysis process to obtain glucose. Dangerous corrosive mineral acids are used, such as hydrochloric acid, which must be very carefully removed from the resulting glucose. The second step is hydrogenation, i.e. glucose is treated with hydrogen to obtain sorbitol.

"In the process we have patented, we follow the same procedure, i.e. we put the cellulose through an acid treatment and hydrogenation. The main difference is that we use carbon dioxide instead of mineral acid, which allows us to activate all the steps in a single facility.The process requires a cellulose-based substrate, which is then treated with water, hydrogen gas and carbon dioxide under specific temperature and pressure conditions. Carbon dioxide is a gas with reactant or solvent properties, and reacts with water to form an acidic solution, carbonic acid. The acidity generated by the combination of water and carbon dioxide ‘releases’ glucose (first step), which with hydrogen turns into sorbitol (second step). In the end, nothing needs to be removed from the compound because the carbon dioxide is released into the atmosphere and the acidity disappears”.

The innovation implemented by the research team does not stop there, as it takes a step further in the direction of sustainable chemistry and circular economy: “We adapted the same process using waste cellulose such as paper, cotton wool, but also a pizza box. Food grade cardboard is required to be fairly pure, and this allowed us to obtain a high sorbitol yield. Now the process is ready to move beyond university laboratories and be applied in industry, where it can be replicated on a large scale”.

Sorbitol: from the current transformation process to the method developed at Ca' Foscari

Ca' Foscari University, through PInK, promotes a culture of Industrial Property that encourages investment in research and development: to this end, it supports organisations and companies in their innovation processes, thus reducing the gap between research and business. PInk accompanies researchers through the patenting process and supports them in building and managing professional relationships.