Possible application of brewer's spent grain in biotechnology/Mogucnosti primene pivskog tropa u biotehnologiji

Brewer's spent grain is the major by-product in beer production. It is produced in large quantities (20 kg per 100 L of produced beer) throughout the year at a low cost or no cost, and due to its high protein and carbohydrates content it can be used as a raw material in biotechnology. Biotechnological processes based on renewable agro-industrial by-products have ecological (zero C[O.sub.2] emission, ecofriendly by-products) and economical (cheap raw materials and reduction of storage costs) advantages. The use of brewer's spent grain is still limited, being basically used as animal feed. Researchers are trying to improve the application of brewer's spent grain by finding alternative uses apart from the current general use as an animal feed. Its possible applications are in human nutrition, as a raw material in biotechnology, energy production, charcoal production, paper manufacture, as a brick component, and adsorbent. In biotechnology brewer's spent grain could be used as a substrate for cultivation of microorganisms and enzyme production, additive or yeast carrier in beer fermentation, raw material in production of lactic acid, bioethanol, biogas, phenolic acids, xylitol, and pullulan. Some possible applications for brewer's spent grain are described in this article, includeing pre-treatment conditions (different procedures for polysaccharides, hemicelluloses and cellulose hydrolysis), working microorganisms, fermentation parameters and obtained yields. The chemical composition of brewer's spent grain varies according to barley variety, harvesting time, malting and mashing conditions, and a quality and type of unmalted raw material used in beer production. Brewer's spent grain is lignocellulosic material rich in protein and fibre, which account for approximately 20 and 70% of its composition, respectively. Keywords: Brewer's spent grain * Biotechnology * Lactic acid * Enzymes * Bioethanol Pivski trop cini najveci deo sporednih proizvoda proizvodnje piva. Na 100 L proizvedenog piva, dobija se oko 20 kg tropa. Trop nastaje u velikim kolicinama tokom cele godine, jeftin je ili besplatan i zbog visokog sadrzaj proteina i ugljenih hidrata moze se upotrebljavati kao sirovina u biotehnologiji. Hemijski sastav pivskog tropa varira od sorte jecma koja se koristi, zatim od vremena zetve, uslova sladovanja i ukomljavanja i tipa i kvaliteta nesladovanih sirovina koje se koriste u proizvodnji piva. Pivski trop je lignocelulozni materijal, bogat proteinima i vlaknima