Enzymatic hydrolysis of pretreated corn cobs and ethanol production by Mucor indicus

Lignocelulozne sirovine poput kukuruznih oklasaka najčešće ostaju neiskorištene, a jeftina su sirovina za proizvodnju biokemikalija kao što je bioetanol. Glavni problem upotrebe takvih sirovina u različitim procesima je potreba provođenja postupaka predobrade i hidrolize koji u konačnici poskupljuju ukupni proces proizvodnje. U ovom radu provedena je enzimska hidroliza (pri 50 °C; pH 4,8) kiselinski predobrađenih kukuruznih oklasaka (s 10-40 g L-1 sirovine) pomoću enzima Viscozyme L i Cellulase, enzyme blend (1-20 % vol vol-1). Stupanj hidrolize od 85 % postignut je kombinacijom 2 % vol vol-1 Viscozyme L i 5 % Cellulase, enzyme blend. Nakon optimizacije enzimske hidrolize, dobiveni hidrolizat korišten je za uzgoj plijesni Mucor indicus te proizvodnju etanola u HRCB-u i barbotirajućem bioreaktoru. Uspješnija proizvodnja bioetanola postignuta je u barbotirajućem bioreaktoru uz ostvarene pokazatelje uspješnosti procesa: YP/S = 0,46 g g-1; Pr = 0,40 g L-1 h-1; E = 90,20 %.Lignocellulosic raw materials like corn cobs are mostly left unused, but they are a cheap raw material for the production of biochemicals, e.g. bioethanol. The main problem with the utilization of such raw materials in different bioprocesses lies in the necessary pretretments and hydrolysis that ultimately increase the cost of the overall production process. In this work, enzymatic hydrolysis (at 50 °C; pH 4.8) of dilute acid pretreated corn cobs (with 10-40 g L-1) was performed using Viscozyme L and Cellulase, enzyme blend (1-20 % vol vol-1). A hydrolysis rate of 85 % was obtained with the combination of 2 % vol vol-1 Viscozyme L and 5 % vol vol-1 Cellulase, enzyme blend. After the optimization of enzymatic hydrolysis, the resulting hydrolysate was used for the cultivation of Mucor indicus and the production of ethanol in HRCB and bubbling bioreactor. Comparing the two production processes, bioethanol production in the bubbling bioreactor was more successful, with the following obtained bioprocess efficiency parameters: YP/S = 0.46 g g-1; Pr = 0.40 g L-1 h-1; E = 90.20 %