Određivanje optimalne pH vrijednosti za rast i proizvodnju etanola s pomoću kvasca Kluyveromyces marxianus NBRC 1777

master's thesis

• Title (english): Determination of optimal pH value for growth and ethanol production by yeast Kluyveromyces marxianus NBRC 1777
• Author: Kristina Vukoje
• Mentor: Antonija Trontel (mentor)
• Committee member: Mario Novak (član povjerenstva)
• Granter: University of Zagreb; Faculty of Food Technology and Biotechnology; (Department of Biochemical Engineering); (Laboratory for Biochemical Engineering, Industrial Microbiology and Malting and Brewing Technology); Zagreb
• Defense date and country: 2021-07-21, Croatia
• Scientific / art field, discipline and subdiscipline: BIOTECHNICAL SCIENCES; Biotechnology

Abstract

U zadnje vrijeme intenzivno se proučava proizvodnja bioetanola iz lignoceluloznih sirovinama s pomoću različitih vrsta mikroorganizama. Hidrolizom lignoceluloznih sirovina dobivaju se fermentabilni šećeri - pentoze i heksoze. Poznato je da kvasac Saccharomyces cerevisiae ne može metabolizirati pentoze, te su stoga istraživanja usmjerena na pronalaženje mikroorganizama koji uz uspješno metaboliziranje pentoza, toleriraju visoke koncentracije etanola i niske pH vrijednosti kakve su prisutne u lignoceluloznim hidrolizatima nakon kiselinskog predtretmana. Kvasac Kluyveromyces marxianus pokazao se kao zadovoljavajuća alternativa kvascu Saccharomyces cerevisiae u procesu proizvodnje etanola. Termotoleratni kvasac Kluyveromyces marxianus može rasti i proizvoditi etanol i pri vrlo niskim pH vrijednostima podloge od 2,3 jedinice. U ovom radu su u svrhu pronalaženja optimalne pH vrijednosti i koncentracije inokuluma za rast i proizvodnju etanola s pomoću kvasca Kluyveromyces marxianus NBRC 1777 provedeni uzgoji u YPD (yeast extract pepton dextrose) podlozi pri pH vrijednostima od 2, 3, 4 i 5 jedinica te uz koncentracije inokuluma od 2,5; 5 i 10 % (vol/vol). Unutar svih testiranih pH vrijednosti, najveća specifična brzina rasta (μ = 0,35 hˉ¹) te najveća produktivnost proizvodnje etanola (Pretanol = 1,51 g Lˉ¹ hˉ¹) i koeficijent konverzije glukoze u etanol (Yetanol/glukoza = 0,50 g gˉ¹), određeni su pri pH vrijednosti od 4 jedinice. Pri pH vrijednosti od 2 jedinice ovaj soj kvasca raste vrlo sporo i proizvodi minimalne količine etanola uz vrlo nisku produktivnost procesa proizvodnje etanola (Pretanol = 0,41 g Lˉ¹ hˉ¹).

Abstract (english)

Recently, the production of bioethanol by microorganisms on lignocellulosic raw materials has been intensively studied. Hydrolysis of lignocellulosic raw materials yields fermentable sugars, pentoses and hexoses. As the yeast Saccharomyces cerevisiae cannot metabolize pentoses, the research is aimed at finding a microorganism that, in addition to successfully metabolizing pentose sugars, tolerates high concentrations of ethanol and low pH values that predominate in hydrolysates after acid pretreatment. The yeast Kluyveromyces marxianus is a suitable alternative to the yeast Saccharomyces cerevisiae in the ethanol production process. Thermotolerant yeast Kluyveromyces marxianus can grow and produce ethanol even at low pH values of the medium of 2.3 units. In this work, in order to find the optimal pH value and inoculum concentration for growth and ethanol production using yeast Kluyveromyces marxianus NBRC 1777, cultivation was performed in YPD (yeast extract peptone dextrose) medium at pH values of 2, 3, 4, and 5 units and with inoculum concentrations of 2.5; 5 and 10 % (vol/vol). Within all tested pH values, the highest specific growth rate (μ = 0.43 hˉ¹) and the highest productivity of ethanol production (Prethanol = 1.51 g Lˉ¹ hˉ¹) plus the conversion coefficient of glucose to ethanol (Yethanol/glucose = 0.50 g gˉ¹), were determined at a pH of 4 units. At a pH value of 2 units, this yeast strain grows very slowly and produces minimal amounts of ethanol with very low ethanol process productivity (Prethanol = 0.41 g Lˉ¹ hˉ¹).

• Keywords: pH vrijednost; koncentracija inokuluma; etanol; glukoza; Kluyveromyces marxianus
• Keywords (english): pH value; inoculum concentration; ethanol; glucose; Kluyveromyces marxianus
• Language: croatian
• URN:NBN: urn:nbn:hr:159:644575
• Study programme: Title: Bioprocess Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka bioprocesnog inženjerstva (magistar/magistra inženjer/inženjerka bioprocesnog inženjerstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2021-10-18 10:35:23