HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Coté, A. Articles by van Walsum, G. P. Search for Related Content PubMed PubMed Citation Articles by Coté, A. Articles by van Walsum, G. P.

Hydrolysis of Lactose in Whey Permeate for Subsequent Fermentation to Ethanol

¹ Department of Chemical Engineering, McGill University, Montreal, QC H3A 2B2
² Tembec Industries Inc., P.O. Box 5000, Témiscaming, QC J0Z 3R0
³ Department of Environmental Studies, Baylor University, P. O. Box 97266, Waco, Texas 76798-7266

Corresponding author: W. A. Brown; e-mail: wayne.brown{at}mcgill.ca.

Fermentation of lactose in whey permeate directly into ethanol has had only limited commercial success, as the yields and alcohol tolerances of the organisms capable of directly fermenting lactose are low. This study proposes an alternative strategy: treat the permeate with acid to liberate monomeric sugars that are readily fermented into ethanol. We identified optimum hydrolysis conditions that yield mostly monomeric sugars and limit formation of fermentation inhibitors such as hydroxymethyl furfural by caramelization reactions. Both lactose solutions and commercial whey permeates were hydrolyzed using inorganic acids and carbonic acid. In all cases, more glucose was consumed by secondary reactions than galactose. Galactose was recovered in approximately stoichiometric proportions. Whey permeate has substantial buffering capacity—even at high partial pressures (>5500 kPa[g]), carbon dioxide had little effect on the pH in whey permeate solutions. The elevated temperatures required for hydrolysis with CO₂-generated inhibitory compounds through caramelization reactions. For these reasons, carbon dioxide was not a feasible acidulant. With mineral acids reversion reactions dominated, resulting in a stable amount of glucose released. However, the Maillard browning reactions also appeared to be involved. By applying Hammet’s acidity function, kinetic data from all experiments were described by a single line. With concentrated inorganic acids, low reaction temperatures allowed lactose hydrolysis with minimal by-product formation and generated a hexose-rich solution amenable to fermentation.

Key Words: lactose hydrolysis • ethanol fermentation • CO₂ hydrolysis • carbonic acid

Abbreviation key: BOD = biological oxygen demand, HMF = hydroxymethylfurfural, PC = principal component, PCA = principal component analysis