Rainhard Koch

Thermoplastic and biodegradable polymers of cellulose

Polymers which are biodegradable currently achieve high interest in materials science since they offer reductions of landfill space during waste management as well as new end-user benefits in various fields of applications. Among these materials, those from renewable resources such as polysaccharides additionally offer CO 2 -neutrality, partial independence from petrochemistry-based products and the exploitation of natures synthesis capabilities via photosynthesis. Cellulose, being a constituent of wood, is regenerated in much larger quantities than starch by natural photosynthesis from CO 2 and water. The very substantial, but so far little exploited category of cellulose-based materials, which has lead to some of the very first industrial polymer-products such as celluloid and cellophane still offers numerous new possibilities for polymeric materials. Basically two main groups of cellulose-materials can be distinguished: regenerated celluloses are suitable only for fibre and film production from conventional and new processes. Secondly, thermoplastically processable cellulose derivatives such as esters can be used for extrusion and moulding. Based on general considerations on the correlation between biodegradability and molecular structure, cellulose derivatives allow both thermoplastic processing and post-consumer waste management via biological decomposition. Ways to realise this demanding new mix of properties considering biodegradability, thermoplastic behaviour and material-properties as well as possible synthetic strategies and their realisation are presented.

BAR 1095 and BAK 2195: completely biodegradable synthetic thermoplastics

BAK-type polyesteramides are new polymers. The combination of high technical performance and full biodegradability is significant for this new generation of thermoplastic materials. All thermoplastic processes such as extrusion, film blowing, film casting, injection molding, blow molding, fiber spinning and others open a wide field of applications.

Biodiversity for biocatalysis: A review of the α/β-hydrolase fold superfamily of esterases-lipases discovered in metagenomes

Abstract Natural biodiversity undoubtedly inspires biocatalysis research and innovation. Biotransformations of interest also inspire the search for appropriate biocatalysts in nature. Indeed, natural genetic resources have been found to support the hydrolysis and synthesis of not only common but also unusual synthetic scaffolds. The emerging tool of metagenomics has the advantage of allowing straightforward identification of activity directly applicable as biocatalysis. However, new enzymes must not only have outstanding properties in terms of performance but also other properties superior to those of well-established commercial preparations in order to successfully replace the latter. Esterases (EST) and lipases (LIP) from the α/β-hydrolase fold superfamily are among the enzymes primarily used in biocatalysis. Accordingly, they have been extensively examined with metagenomics. Here we provided an updated (October 2015) overview of sequence and functional data sets of 288 EST–LIP enzymes with validated functions that have been isolated in metagenomes and (mostly partially) characterized. Through sequence, biochemical, and reactivity analyses, we attempted to understand the phenomenon of variability and versatility within this group of enzymes and to implement this knowledge to identify sequences encoding EST–LIP which may be useful for biocatalysis. We found that the diversity of described EST–LIP polypeptides was not dominated by a particular type of protein or highly similar clusters of proteins but rather by diverse nonredundant sequences. Purified EST–LIP exhibited a wide temperature activity range of 10–85 °C, although a preferred bias for a mesophilic temperature range (35–40 °C) was observed. At least 60% of the total characterized metagenomics-derived EST–LIP showed outstanding properties in terms of stability (solvent tolerance) and reactivity (selectivity and substrate profile), which are the features of interest in biocatalysis. We hope that, in the future, the search for and utilization of sequences similar to those already encoded and characterized EST–LIP enzymes from metagenomes may be of interest for promoting unresolved biotransformations in the chemical industry. Some examples are discussed in this review.