Research
Climate change, greenhouse gas emissions, and growing scarcity and rising prices of fossil fuels: These are the global challenges we currently face. Increased material and energetic utilisation of renewable resources and available residual biomass have become absolutely essential, from both an ecological and an economic standpoint. Intense research and development work on biomass utilisation lays the foundation for efficient and cost-effective exploitation of these resources.
The research activities of PFI Biotechnology’s interdisciplinary team of biotechnologists, microbiologists, chemists, and engineers are focussed on the areas of biogas, fermentation, and biomass pretreatment.
Biogas
Biogas
Optimisation of Process Biology
A principal task of PFI Biotechnology is to initiate and implement research projects in the area of biogas. In current projects we are studying the microbial flora in biogas plants. Optimisation of process biology offers enormous potential for further efficiency enhancements in biogas generation.
Our goal is to elucidate the manifold interactions between the central microbial groups in the biogas process and to acquire a more profound understanding of the optimum growth and nutrient conditions.
Isolation and characterisation of particularly effective bacteria also opens up the possibility of developing starter cultures specifically for biogas plants.
Utilisation of Residual Biomass – Lignocellulose
Another important field of research for PFI Biotechnology is the assessment of the suitability of hitherto hardly utilised kinds of biomass as a substrate for biogas generation. The main focus is on residual biomass and agricultural co-products such as material from landscape management or straw. Increased use of these substrates could defuse the conflict as to whether agricultural land is used to grow energy crops or food crops.
However, the use of such highly lignified biomass in biogas plants poses new challenges for process engineering and process biology. We are developing and optimising new digestion methods to transform these materials into substrates suitable for biogas generation (see also Pretreatment of Biomass).
Nutrient Optimisation
We also test the effect of additives on the biogas process. One important current topic is that of providing microorganisms with an adequate supply of trace nutrients, especially in plants with high volumetric loading rates and little or no liquid manure in the substrate mix. We investigate which trace elements are of crucial importance for process stability in biogas plants, and determine their optimum concentrations.
Cost-benefit analysis on use of hydrolytic enzymes in biogas plants is the topic of an extensive joint project with participation of PFI Biotechnology.
Fermentation
Fermentation
Material utilisation of renewable resources in the form of a bio-based chemical and polymer production will become hugely important in the future. Whereas various possibilities exist for the substitution of fossil fuels in the energy and transport sectors, the only future alternative available for the polymer sector is biomass. Our goal is to shed light on the complex interactions between the key microbial groups in the biogas process and to gain a deeper understanding of the optimal growth and nutrient conditions. The isolation and characterisation of particularly efficient bacteria also open up opportunities for the development of starter cultures specifically tailored to biogas plants.
Fermentative Production of Biopolymers
A key focus of activity at PFI Biotechnology is the fermentative production of biopolymers for substitution of petroleum-based plastics.
We are currently conducting research on the production of polyhydroxybutyric acid (PHB) and other polyhydroxyalkanoates (PHA) by means of specific bacterial strains. PHB, PHB copolymers, and other PHAs are intracellular storage substances accumulated by various microorganisms. They can be used to produce thermoplastic biopolymers with excellent material properties which can easily hold their own in competition with petroleum-based plastics such as polyethylene (PE) or polypropylene (PP). In contrast to the latter, however, they are completely biodegradable and can be composted.
Broad application of biopolymers is offset by their still very high prices. These are due, on the one hand, to the cost of raw materials because they are currently produced mainly from sugars (fructose or maltose); on the other hand, separation and purification of PHB from cellular material incur relatively high processing costs.
PHB from Residual Biomass
PFI Biotechnology is therefore pursuing the goal of producing PHB from low-cost residual biomass such as straw. A combination of thermal and enzymatic digestion processes transforms hemicelluloses and lignocellulose into a form suitable for fermentation. Energy for the process is provided by biogas generation from residual materials. In parallel we are investigating new approaches to solvent-free isolation of the target product.
C5 Fermentation
Other research projects include fermentations on the basis of pentoses from hydrolysed hemicelluloses. Production of the valuable sugar alcohol xylitol from xylose with the aid of special yeasts is a key area of activity.
Pretreatment of Biomass
Pretreatment of Biomass
Process-controlled Enzymatic Hydrolysis (PEH)
The degree and rate of degradation of substrates in the biogas process are strongly dependent upon the chemical structures of the materials involved. Whereas fats, proteins, and starch are very rapidly and almost completely transformed into biogas, the fibrous components, and especially the cellulose fraction, pose a challenge for biogas generation. On the one hand, the structure of the cellulose fibres hinders enzymatic hydrolysis; on the other hand, the conditions typically encountered in a biogas digester (pH value, temperature) are unfavourable for cellulolytic enzymes and significantly reduce their activity. Fibrous plant components are consequently degraded only slowly and incompletely in biogas plants.
Against this backdrop, PFI Biotechnology has developed a special pre-hydrolysis process to substantially increase the degree and rate of degradation of the fibrous components. In process-controlled enzymatic hydrolysis (PEH) the biomass is pretreated in a specially designed hydrolysis vessel before it reaches the biogas digester. Optimum pH and temperature condition for the activity of hydrolytic enzymes are maintained in this controlled and sensor-monitored process. After thorough laboratory and pilot-scale testing, the process is currently undergoing full-scale trials (see also Development).
Thermal Pressure Hydrolysis (TPH)
Use of lignified biomass requires the application of further pretreatment processes, especially if sugar-enriched hydrolysates are to be provided for fermentation.
Here PFI Biotechnology is working hard on a hydrothermal pretreatment process, known as Thermal Pressure Hydrolysis (TPH). The hemicellulose fraction of lignified substrates (such as straw) is extensively hydrolysed in a special batch process and the lignocellulose prepared for subsequent enzymatic hydrolyse (see also Development).
Lignocellulose: is the most widely distributed of all naturally occurring organic materials and is the primary building block of plant cell walls. The three major components of lignocellulose are: cellulose, hemicellulose, and lignin. These three biopolymer structures are together responsible for the stability of plant materials. For example, the pronounced durability of wood is attributable to these substances.
Above all, lignin is particularly stable and protects plant structures against microbial degradation. However, it is precisely this persistence which hinders the biotechnolocal transformation of lignocellulose into chemical raw materials, fuels (2G), energy, etc.
Sustainable conversion of lignocellulose requires mixtures of enzymes which hydrolyse cellulose and hemicellulose into their component sugars. At present these enzymes are very costly to produce. Industrial-scale implementation of the processes is therefore currently uneconomical.
2G Fuels: Biofuels – i.e. fuels derived from biomass – can nowadays be divided into two categories: If substrates containing sugar or starch, e.g. maize or sugar cane, are used in their production, they are described as 1st generation (1G) biofuels. Such 1G fuels are comparatively easy to produce and are manufactured on an industrial scale, for example in the USA and Brazil (bioethanol). However, their popularity is steadily declining because the land used for growing fuel crops cannot be used for cultivation of food crops.
Intense research is therefore being conducted on the production of fuels from residual biomass such as straw. Residual biomass consists mainly of lignocellulose and is not suitable for consumption as food or animal feed. Fuels derived from lignocellulose are designated as 2nd generation (2G) fuels. Their industrial production is currently very expensive. The main cost drivers are the enzymes used in their production process (see lignocellulose).
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