Appl Microbiol Biotechnol (2004) 66: 1–9 DOI 10.1007/s00253-004-1714-3 MINI-REVIEW Johann Plank Applications of biopolymers and other biotechnological products in building materials Received: 28 May 2004 / Revised: 8 July 2004 / Accepted: 9 July 2004 / Published online: 1 October 2004 # Springer-Verlag 2004 Abstract Bio admixtures are functional molecules used in building products to optimize material properties. They include natural or modified biopolymers, biotechnological and biodegradable products. Concrete and dry-mix mortars (e.g. wall plasters or tile adhesives) represent two major applications for bio admixtures. Examples of bio products used in concrete are lignosulfonate, sodium gluconate, pine root extract, protein hydrolysates and Welan gum; and in dry-mix mortar methyl hydroxypropyl cellulose, hydroxypropyl starch, guar gum, tartaric acid, casein, succinoglycan and Xanthan gum. In a number of applications, bio admixtures compete well with synthetic admixtures. Sometimes, they are indispensable in the formulation of certain building products. Their market share is expected to increase because of technological advances, particularly in the field of microbial biopoly- mers, and because of the growing trend to use naturally based or biodegradable products in building materials. Introduction The benefit from using admixtures in building materials to improve their properties was discovered in ancient times. As early as 3000 B.C., the Sumerians used bitumen as an organic binder and water-repellent in mixtures with clay and straw. Being magnificent architects, the Romans required highly advanced building materials and invented the use of particular chemicals obtained from natural sources. For example, in his famous encyclopedia “De architectura libri decem”, Vitruvius (84–10 B.C.) de- scribed the use of biopolymers such as proteins for set retardation of gypsum and dried blood for air-entrainment (Vitruvius Pollio 2001). Today, admixtures providing additional properties such as plastification, water retention, adhesion, shrinkage reduction etc. are available to the building materials industry. In 2000, the global market volume for chemical admixtures in building materials was estimated at approximately U.S. $ 15×10 9 (Becker, personal commu- nication). Of this, roughly U.S. $ 2×10 9 were for bio admixtures (Plank 2003). Their relative market share in comparison with synthetic chemicals has increased over the past 10 years. With environmental awareness for constituents in building materials generally growing, the trend towards bio admixtures is expected to continue. The term “bio admixture” as used in this review comprises biopolymers and products produced by bio- technological processes. Admixtures produced in biotech- nological processes are meant to be products made in fermentation processes by employing bacteria or fungi. Synthetic admixtures with significant biodegradability, such as polyaspartic acid, are also perceived as bio admixtures by the industry and are therefore included. Bio admixtures might be small molecules, such as tartaric acid or sodium gluconate, or macromolecular compounds, such as lignosulfonate, cellulose ether or Xanthan gum. Some- times they are native products isolated from natural sources and used as is (“natural products”), or they are chemically modified by derivation from natural products, e.g. to introduce specific chemical groups into the molecule, or they are processed, for example, to adjust the molecular weight for optimized performance. Product overview A great diversity of bio admixtures with well over 500 different products is used by the building materials industry. Table 1 gives an overview of products with either significant market volume or major technological impact. Among them are products obtained from plants (e.g. starch), animal sources (e.g. casein), soil (e.g. humic J. Plank (*) Chair for Construction Chemicals, Institute for Inorganic Chemistry, Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany e-mail: johann.plank@bauchemie-tum.de Tel.: +49-89-28913150 Fax: +49-89-28913152