| Abstract | Otpadne lignocelulozne sirovine, u odnosu na šećerne i škrobne sirovine koje se uvelike koriste za prehranu ljudi i životinja, predstavljaju održivu alternativu za proizvodnju biokemikalija kao što je mliječna kiselina. U ovom radu provedena je predobrada pšenične slame s 2 %-tnom natijevom lužinom u visokotlačnom reaktoru pri različitim temperaturama (120°C-210°C) i vremenima zadržavanja od 1 do 20 minuta. Nakon predobrade pšenične slame, dobivene su dvije faze (čvrsta i tekuća faza) te je određen njihov sastav. Čvrsta faza (predobrađena pšenična slama) koja se sastoji većinom od glukana (wglukan = 87,36 %) korištena je za hidrolizu komercijalnim celulazama i b- glukozidazom izoliranim iz plijesni Aspergillus niger. Nakon optimizacije enzimske hidrolize, dobiveni hidrolizati korišteni su za proizvodnju mliječne kiseline s pomoću bakterije mliječne kiseline Lactobacillus amylovorus DSM 20531T. Provedena je i simultana hidroliza s celulazama i b- glukozidazom iz plijesni A. niger i fermentacija predobrađene pšenične slame do mliječne kiseline pomoću L. amylovorus DSM 20531T, pri čemu su ostvareni ovi pokazatelji uspješnosti procesa: YP/S = 0,30 i 0,33 g g-1, PrMK = 0,23 i 0,24 g L-1 h-1, μm = 0,30 i 0,31 h-1 (celulaze, celulaze + β-glukozidaza). |
| Abstract (english) | Residual lignocellulosic biomass, in contrast to sugar and strach containing raw materials which are widely used as food and feed, represents sustainable alternative for production of biochemicals, e.g. lactic acid. In this work, alkali pretreatment of wheat straw with 2 % sodium hydroxide solution in high-preasure reactor at different temperatures (from 120°C to 210°C) and residence times (from 1 to 20 minutes) was performed. After alkali pretreatment of wheat straw, solid and liquid phase were obtained and composition of the two phases was determined. Solid phase (pretreated wheat straw), comprised mostly of glucans (wglukan = 87,63 %), was used for hydrolysis with commercial cellulases and b-glucosidases isolated from mold Aspergillus niger. After optimization of enzymatic hydrolysis, obtained hydrolysates were used for lactic acid production by lactic acid bacterium Lactobacillus amylovorus DSM 20531T. Additionaly simultaneos hydrolysis with commercial cellulases and b- glucosidases isolated from A. niger of solid phase obtained after the pretreatetment of wheat straw and fermentation of simpler carbohydrates to lactic acid by L. amylovorus DSM 20531T, where fallowing values of bioprocess efficiency parameters where obtained : YP/S = 0,30 and 0,33 g g-1, PrMK = 0,23 and 0,24 g L-1 h-1, μm = 0,30 and 0,31 h-1 (cellulases, cellulases and b-glucosidases). |
