The effect of Mn2+ on ethanol production from lactose using Kluyveromyces marxianus IMB3 immobilized in magnetically responsive matrices

Abstract

The thermotolerant, ethanol producing yeast strain, K. marxianus IMB3 was immobilized in calcium alginate containing magnetically responsive Fe 3 O 4 particles. In these studies the -galactosidase derived from K. marxianus IMB3 was immobilized onto the Fe 3 O 4 particles prior to inclusion into the alginate matrix. Ethanol production by the immobilized microorganism in the presence of Fe 3 O 4 reached a maximum of 16 g/L on 40 g/L lactose whereas prior immobilization of the enzyme to the particles and inclusion into the alginate matrix increased ethanol production to a maximum concentration of 18 g/L. When Mn 2+ was incorporated into fermentations containing the immobilized enzyme in the alginate matrix, ethanol production increased further to a maximum concentration of 20 g/L. In addition, the behaviour of the magnetically responsive biocatalyst containing the co-immobilized enzyme was examined in a batch-fed system in the presence and absence of Mn 2+ .

Magnetically responsive yeast cells: Methods of preparation and applications

“…The same observation was made for the fermentation capacity and alcohol production, which were not influenced in the case of S. cerevisiae cells immobilized in calcium alginate gel together with varying concentrations of magnetic iron oxides or ferrites (Ivanova et al ., ; Larsson and Mosbach, ). The production of ethanol by K. marxianus IMB3 immobilized in calcium alginate increased substantially when magnetite particles with immobilized β ‐galactosidase derived from the same strain were co‐immobilized; the ethanol production increased further when Mn 2+ ions were incorporated into fermentation media (Brady et al ., ). Ethanol fermentation with magnetically modified S. cerevisiae cells was also performed in magnetically stabilized fluidized‐bed reactors (Ivanova et al ., ; Liu et al ., ).…”

The effect of soluble alginate and calcium on β-galactosidase activity produced by the thermotolerant, ethanol-producing yeast strain Kluyveromyces marxianus imb3

“…It has also been demonstrated that productivity of ethanol from lactose-containing media may be enhanced by supplementation of the immobilized preparations with K. marxianus IMB3 b-galactosidase activity [9]. In addition, to the advantages associated with biocatalyst re-use in the above described systems it was also found that productivity of ethanol over long periods of time was also enhanced, particularly in batch-fed bioreactor con®gurations [10]. During many of those experiments it became apparent that the biocatalyst appeared to be stabilized to some degree and it was suggested in the absence of further data at that time that this stabilization may have been attributed to the alginate matrix itself.…”

“…As mentioned above the thermotolerant, ethanol-producing yeast strain Kluyveromyces marxianus IMB3 has been shown to exhibit enhanced ethanol production in a variety of alginate-based immobilization systems during growth on lactose-containing media at 45°C [7,8,9,10]. In certain cases it has been found that the life-time of the biocatalyst has been extended considerably following immobilization and it has been suggested that some of the immobilized systems and con®gurations might play a role in commercial processes concerned with the conversion of lactose-containing dairy wastes to ethanol.…”

“…In certain cases it has been found that the life-time of the biocatalyst has been extended considerably following immobilization and it has been suggested that some of the immobilized systems and con®gurations might play a role in commercial processes concerned with the conversion of lactose-containing dairy wastes to ethanol. During some of our earlier studies it was suggested that the alginate matrix may have been stabilizing either the functionality of the yeast with respect to ethanol production or contributing positively to the stability of the K. marxianus IMB3 cellassociated b-galactosidase [10]. It has been shown that Mn 2+ has a very signi®cant enhancing effect on ethanol production by this yeast strain [10] and it was subsequently shown that the b-galactosidase activity is stabilized and activated at 45°C in the presence of that ion [10].…”

“…During some of our earlier studies it was suggested that the alginate matrix may have been stabilizing either the functionality of the yeast with respect to ethanol production or contributing positively to the stability of the K. marxianus IMB3 cellassociated b-galactosidase [10]. It has been shown that Mn 2+ has a very signi®cant enhancing effect on ethanol production by this yeast strain [10] and it was subsequently shown that the b-galactosidase activity is stabilized and activated at 45°C in the presence of that ion [10]. Since all of our immobilization systems are carried out in media supplemented with free Ca 2+ in order to maintain structural integrity of the alginate matrix and since it was found that Mn 2+ stabilized the enzyme, it was decided to examine the thermal stability of the enzyme in the presence of Ca 2+ .…”