| Abstract | Pivski trop kao lignocelulozna sirovina predstavlja obnovljiv, jeftin i lako dostupan izvor ugljika i energije za dobivanje visokovrijednih proizvoda kao što su biokemikalije i biogoriva. U ovom radu istraživana je sposobnost rasta i sinteze vrijednih proizvoda metabolizma (2,3-butandiola, etanola, mliječne kiseline, acetoina, lignocelulolitičkih enzima) bakterije Paenibacillus polymyxa DSM 742 na kemijski definiranim podlogama i različitim hidrolizatima dobivenim predobradom pivskog tropa. Uzgojem u podlozi s 10 g/L kvaščevog ekstrakta (kao izvora dušika) postignut je najviši prinos 2,3-butandiola, dok su najviši prinosi etanola i acetoina postignuti uzgojem u podlozi s 10 g/L peptona. Najveća enzimska aktivnost (3,31 U/ml) zapažena je tijekom uzgoja na ksilanu kao izvoru ugljika. Šaržnim uzgojem s pritokom supstrata, u bioreaktoru s miješalom, u podlozi koja simulira kiselinski hidrolizat pivskog tropa proizvedeno je 91,702 g 2,3-butandiola, 114,398 g mliječne kiseline, 67,845 g etanola i 16,224 g acetoina, što je značajno više u odnosu na šaržni način vođenja procesa. Šaržnim uzgojem s pritokom supstrata u bioreaktoru s miješalom, na kiselinskom hidrolizatu, glavni produkt bio je etanol (67,552 g), a ostali produkti metabolizma sintetizirani su u manjim količinama. Uzgojem na enzimskom hidrolizatu čvrste faze zaostale nakon kiselinske hidrolize proizvedena je jedino mliječna kiselina (183,776 g). |
| Abstract (english) | Brewers' spent grain (BSG), as a lignocellulosic material, represents a renewable and cheap carbon source to obtain high-value products such as biochemicals and biofuels. The aim of this study was to investigate growth and production potential of valuable products (2,3-butanediol, ethanol, lactic acid, acetoin, lignocellulolytic enzymes) of the bacterium Paenibacillus polymyxa DSM 742 in chemically defined media and different hydrolysates of pretreated BSG. The highest yield of 2,3-butanediol was obtained during the cultivation in the media with 10 g/L yeast extract (as a nitrogen source), while the highest yields of ethanol and acetoin were achieved during the cultivation with 10 g/L peptone. The highest enzyme activity (3.31 U/ml) was observed during the cultivation with xylan as a carbon source. During the fed-batch cultivation in a stirred tank bioreactor (STBR), in the media that simulates the acid hydrolysate of pretreated BSG, 91.702 g of 2,3-butanediol, 114.398 g of lactic acid, 67.845 g of ethanol and 16.224 g of acetoin were produced, which is significantly higher compared to the batch cultivation. The main product obtained during the fed-batch cultivation in the STBR, on acid hydrolysate was ethanol (67.552 g), while other products were produced in smaller quantities. The only product obtained during the cultivation in the liquid phase of enzymatically hydrolyzed solid part of pretreated BSG was lactic acid (183.776 g). |
