Study in Chemical Reviews written exclusively by BME researchers

The university’s experts gave an overview of the latest advances in sustainability and the chemistry of carbohydrates in the journal of the American Chemical Society.

The notions of “green” chemistry, sustainable chemistry and sustainable development are hot topics these days: they are often confused, especially, when used with such expressions as biomass and renewable raw materials, stressed László Tamás Mika, Head of the Department of Chemical and Environmental Process Engineering at the Faculty of Chemical Technology and Biotechnology. He and his colleagues have recently published a study on the subject in the renowned journal, Chemical Reviews. He added: ‘the representatives of green movements often think that all of mankind’s energy and raw material needs can be solved with renewable energy resources or chemical industry raw materials in the future, however, the issue is far from being so clear-cut. It is important to base any predictions regarding sustainability on sound calculations and proper scientific studies’. This is where the journal’s thematic issue can be useful, where a part of the broader topic, related to carbohydrates, as well as the relevant sustainability indices are summarised together with co-authors Edit Cséfalvay, associate professor of the Department of Energy Engineering at the Faculty of Mechanical Engineering and Áron Németh, assistant professor of the Department of Applied Biotechnology and Food Science at the Faculty of Chemical Technology and Biotechnology.

Chemical Reviews is the monthly journal of the American Chemical Society, issued since 1924. The peer-reviewed journal’s impact factor is 47.9, making it the most renowned forum in its field. (Editor notes: The impact factor is used to measure scientific performance and is based on the analysis of citations to a journal. It shows the average number of citations in the current year to items published in the previous two years).

The thematic issue on sustainable chemistry was edited by István Tamás Horváth, Chair Professor of the Department of Chemistry, City University of Hong Kong, BME’s Honorary Professor and internationally acknowledged expert of the field. The almost 800-page issue contains eight reviews on the most important results of the literature on biomass-based energy sources and chemical industry raw materials, published in the last few years; discussing such issues as energy storage, the role of water as a solvent, the depolymerisation of lignin, a major component of biomass, solvents that are widely used in the chemical industry, the conversion of carbon dioxide, polymer chemistry and biocatalysis, without which the modern pharmaceutical industry, chemical industry and food industry would not exist.

This is the second time that one of the journal’s papers was written exclusively by BME’s professor-researchers. The title of the 108-page study which includes 762 citations: Catalytic Conversion of Carbohydrates to Initial Platform Chemicals: Chemistry and Sustainability.

My research group has been studying biomass-based platform molecules for eight years, looking at the best ways to improve their production and exploring new areas of use, which led to the task of reviewing the conversion of carbohydrates’, recalled László Tamás Mika.

We were invited to give a critical analysis and summarise the latest results of the literature from the last few years. It soon turned out that the vast number of papers could not be reviewed and selected by one person only; it required faculty- and department-wide collaboration. We also realised that chemistry on its own is not enough to understand and analyse sustainability. These sustainability aspects have been reviewed by Edit Cséfalvay, the researcher explained. ‘Since certain platform molecules cannot be produced without biotechnology, we turned to Áron Németh, with whom we had worked in the past’, he added.

Platform molecules – parent compounds – are building blocks: they include many complex types of materials, which can be further intermediate or finished products. Classic petrochemical industry only uses a small number of platform molecules, the most important of which are benzene, toulene, xylenes, ethylene, propylene, butadiene and synthesis gas (CO, H2). Biomass-based chemistry uses a much wider range of compound groups; these are currently a hot topic both in domestic and international research. For example, in 2013 alone a 100-page summary paper, built on 543 citations, was published on one of the platform chemicals, the 5-Hydroxymethyl-2-furfural molecule’, said László Tamás Mika describing the vast interest in the field. The difficulty was to narrow down the literature according to the correct criteria, he said of one of the biggest challenges.

How can we summarise the issue of chemistry and sustainability?, asked the researcher, adding that the foundations are governed by the rules of chemistry and thermodynamics. The authors relied on chemical and biotechnological reaction mechanisms as an objective basis to select the relevant results. Equilibrium reactions, energy levels and thermodynamics define sustainability on a molecular level. ‘For example if I have 50% by-product from a procedure, I will never achieve a 100% yield from a particular product’, the professor stated in illustration of the above. He added: ‘this was one of our filter criteria during the selection of the studies: we only included one or two especially interesting cases from the procedures with less than 50% yield.

The subchapters of the paper followed a clearly defined structure: after the initial brief introduction on the given platform molecule and its history, its industrial use was discussed, followed by detailed economic indicators. Then the reaction mechanisms related to its production, in other words the theoretical potentials within chemistry, were summarised, after which scientific and technical production options, steps and challenges were looked at. Sections on the fundamental biotechnology researches also included the latest genetic results and findings, followed by a conclusion and an outlook.

‘Sustainability is built on the fundamentals of energetics and thermodynamics, which are my fields of expertise at the Department of Energy Engineering’, said Edit Cséfalvay, also confirming that the biggest challenge was the proper selection of the papers: in her field for example, they used over 500 various indicators. She explained that her task was to collect and evaluate measures which had been previously established by researchers for products, procedures and reactions from biomass processing. ‘Although 99% of the study is a review, which is basically a summary, I also included our research on ethanol equivalents, which we had previously conducted with Professor Horváth and had proved very useful’, she explained to

Ethanol equivalent (EE) is defined as the mass of ethanol (in kilograms, tonnes or million tonnes), needed to deliver the equivalent amount of energy from a given feedstock or produce the equivalent amount of mass of a carbon-based chemical. EE gives a numeric value on the sustainability of molecules, therefore it can be used as a “translational tool” to compare fossil- and biomass-based feedstocks and products, processes, and technologies. It can also clearly demonstrate the size of land to be planted with corn in order to produce the required amount of ethanol. The article’s reviewers welcomed the introduction of this new indicator. ‘This measure gives us objective thermodynamics values, devoid of political, social or economic interests, to help us determine the sustainability of a given product or chemical process’, explained Edit Cséfalvay.

Áron Németh was tasked with the review of the biology and biotechnology literature. ‘My research group in the Fermentation Pilot Plant Laboratory is involved in applied microbiology and its industrial application’, he explained, adding that ‘in our paper we focused on platform molecules, but we could have studied the production of materials with smaller volume, but yielding higher added value, such as prebiotics, vitamins, hormones, pesticides, etc. We had to narrow down our focus, which was difficult’.

The researcher opened up new perspectives in his field of expertise toward new advances in genetics, where basically everything can be transformed into another compound. Modified gene products (proteins, enzymes) can create reaction paths which otherwise would not occur in nature. This leads to complex systems, new or modified metabolic pathways, the literature of which is very extensive. ‘Initially I set out to put together a table by examining all the microorganisms that are important in the industry, but this would have been so big, that I had to narrow it down. I decided to consider only research within biotechnology which is very close to industrial application or has already been implemented. A great lesson for us was to learn selective reading’, admitted Áron Németh.

BME’s professor-researchers worked on refining their paper after the review phase for another two months. ‘I have already incorporated the conclusions of the study into my autumn-term courses’, said László Tamás Mika, pointing out the benefits of academic utilisation of the findings. He emphasised: ‘apart from the basic curriculum, learning about the latest international findings is also important for the students, for which this paper provided an excellent opportunity. To the best of our knowledge there are no summary publications which discuss both biochemical and classical catalytic chemical conversions. We hope that apart from chemists and chemical engineers, our paper will be useful for professionals who study sustainability in a wider sense.


Photo: János Philip