From malic acid to bio-surfactants and polyesters
Researchers at Fraunhofer IGB produce a wide variety of chemicals using fungi. One example is malic acid. There is a continually growing market for the substance, which gives products such as jams and juices a sour taste and improves the shelf life of baked goods. It can also be used as a building block for bio-based polyesters. And, in a process similar to brewing beer, it can be produced using molds. In beer brewing, the yeast ferments the malt sugar of the barley, while in malic acid production Aspergillus fungi convert sugar or vegetable oils.
This can be done by “feeding”, for instance, a wood-based sugar solution to the fungi to get them to generate malic acid. Fermentation like this works well on a laboratory scale. The IGB researchers are currently investigating ways to scale up the process for commercialization, in particular, by improving the fermentation yield.
Using a similar process, they can also create surface-active agents that can be used to produce detergents, emulsifiers, active ingredients for cosmetics, pharmaceutics, and pesticides. That’s where the smut fungi come into play. They’re parasites that infest plants, making them look like they’ve been burned – hence their Germanic name, Brandpilze [burnt fungi]. “The process is another one we’re actively developing for industrial production. Our principal goal is to optimize the composition of the biosurfactants we produce to suit various applications in the field of detergents and emulsifiers,” explains Dr. Susanne Zibek, head of the Industrial Biotechnology Group.
Yeasts are also interesting producers. In addition to brewing beer, as previously mentioned, certain yeasts can also be used to produce molecules that are essential for synthesizing novel plastics, such as long-chain dicarboxylic acids. The researchers at Fraunhofer IGB have succeeded in working out a process to produce long-chain dicarboxylic acids from a strain of Candida.
Scaling up: the Fraunhofer pilot plant and biorefinery
If the bio-based chemicals are to be used in industrial applications – whether as surfactants, as food components such as malic acid, or as molecular building blocks for plastics – they’ll need to be synthesized on a large scale. This is a daunting challenge: the worldwide production of surfactants, for instance, is 18 million metric tons per year. “Scaling-up the processes from kilograms to tons involves a great deal of engineering and computing,” explains Zibek. There are still questions that need to be answered: How do we perfect the composition of the fermentation media? What’s the best way to feed the fungi? Fraunhofer Researchers are initially addressing such questions on a small scale.
Once this hurdle has been cleared, the researchers at the Fraunhofer Center for Chemical-Biotechnological Processes CBP will then need to establish the processes for large-scale production. They operate a pilot plant in which the fermentation processes can be scaled up to a maximum of ten cubic meters. Such a huge volume requires an enormous amount of raw materials; after all, the fungi need feeding. The preferred source for the scientists is wood sugar, in other words, sugar solutions that contain both glucose and xylose. These can be obtained directly in the Fraunhofer CBP ligno-cellulose biorefinery and mixed into the culture medium.
In turn, this provides the molds and other fungal organisms with optimal growth conditions using renewable raw materials, allowing them to produce tons of chemicals.
The Fraunhofer-Gesellschaft is the leading organization for applied research in Europe. Its research activities are conducted by 72 institutes and research units at locations throughout Germany. The Fraunhofer-Gesellschaft employs a staff of more than 25,000, who work with an annual research budget totaling 2.3 billion euros. Of this sum, almost 2 billion euros is generated through contract research. Around 70 percent of the Fraunhofer-Gesellschaft’s contract research revenue is derived from contracts with industry and from publicly financed research projects. International collaborations with excellent research partners and innovative companies around the world ensure direct access to regions of the greatest importance to present and future scientific progress and economic development.