Renewable raw materials
Plants photosynthetically form a huge, so far only incompletely used spectrum of different chemical compounds. Starting materials for industrial biotechnology are primarily agricultural products such as cereals, legumes or oil plants. These biogenic raw materials are not completely constant in composition and raw material content, but vary slightly – depending on variety and cultivation conditions.
The content of special metabolites for "building blocks" or as a substrate for bioconversion depends both on the plant species and the extent of breeding work. Valuable plant substances for industrial biotechnology are mainly oils and fats as well as polysaccharides, but also polyoses and various secondary plant substances, such as phenolic acids, flavonoids, glucosinolates, isoflavones, lignans or pigments.
Various raw material sources for the production of biobased chemicals have already been intensively examined, for example lignocelluloses, carbohydrates, fats and oils as well as microalgae. Biogas, synthesis gas and CO2 also play an increasing role.
||Raw and Residual materials
|straw | oil seeds
||lignocellulose | oils
|algae | crab shells
||carbohydrates, proteins, lipids | chitin
|CO2, waste wood, black liquor, food residues
||pomace, fruit and vegetable waste, crab shells
||insects, crab shells, meat-and-bone meal
||animal fats, extracts
In order to make the raw material components accessible to the microorganisms or enzymes, several processing stages have to be passed through, depending on the type of starting material. These are mechanical, thermal or chemical processes which have to be adapted to the subsequent bioconversion.
Residual materials, such as those generated in agriculture or food production, often still contain useful metabolites. A major focus at the IGB is on intensifying the use of residual and waste streams. With integrated bioprocesses, in which special microorganisms or biocatalysts convert individual, valuable substances in a targeted and specific way, waste disposal can be combined with the production of valuable materials. One example is sour whey, a residue from milk processing that still contains a lot of lactose. This can be converted into lactic acid by a combination of fermentation and various membrane processes such as filtration and electrodialysis and recovered as a product. Lactic acid can be used as a basic chemical in the chemical industry or further refined directly by polymerization to polylactide, a biodegradable plastic.
Another waste product that occurs in large quantities is crab shells from aquaculture or insect exuviae from the protein production of animal feed. These contain chitin, the most common biopolymer after cellulose. Fraunhofer IGB has identified microorganisms and enzymes as part of various projects with the aim of first purifying chitin as a raw material source and developing it for conversion to chitosan or chitin oligomers as well as the monomer. In addition, functional groups can be introduced to enable new properties, e.g. for a functional finishing of textiles.
Particular attention should be paid to lignocellulosic raw materials – wood or straw as residues from agriculture and forestry. These are currently still mainly used for the production of energy (combustion) or cellulose, as the compound of cellulose, hemicellulose and lignin cannot be used for biotechnological or chemical conversion without suitable pretreatment. Specially developed mechanical-chemical pulping and fractionation processes also allow lignocellulosic raw materials such as wood or straw to be used effectively as materials. In national collaborative projects such as the lignocellulose biorefinery, Fraunhofer CBP has further developed the organosolv process developed at Fraunhofer ICT and successfully implemented it on a pilot plant scale. In parallel, Fraunhofer IGB has optimized and scaled up a biotechnological approach for the enzymatic digestion of sugars from pretreated lignocellulose from wood waste or straw. In addition, new enzymes for the functionalization of lignin building blocks were characterized.