Study of whey fermentation by kefir immobilized on low cost supports using 14 C-labelled lactose Magdalini Soupioni a,⇑ , Aristidis Golfinopoulos a , Maria Kanellaki b , Athanasios A. Koutinas b a Nuclear Chemistry Group, Department of Chemistry, University of Patras, GR-26500 Patras, Greece b Food Biotechnology Group, Department of Chemistry, University of Patras, GR-26500 Patras, Greece highlights " 14 C-labelled lactose uptake rate by kefir immobilized on BSG and MSR was studied. " Lactose uptake rate by immobilized cells was correlated to fermentation rate in whey. " Biocatalysts with low cost BSG, MSR, GP or DCM increase the whey fermentation rate. " BSG cellulosic biocatalyst can in 8 h ferment the lactose of whey and produce alcohol. " Hydrophilic cellulose protects immobilized cells and increase biocatalytic activity. article info Article history: Received 16 October 2012 Received in revised form 17 December 2012 Accepted 19 December 2012 Available online 7 January 2013 Keywords: 14 C-labelled lactose Kefir Whey fermentation Brewer’s Spent Grains (BSG) Malt Spent Rootlets (MSR) abstract Brewer’s Spent Grains (BSG) and Malt Spent Rootlets (MSR) were used as supports for kefir cells immo- bilization and the role of lactose uptake rate by kefir in the positive activity of produced biocatalysts dur- ing whey fermentation was investigated. Lactose uptake rate by the immobilized cells was recorded using 14 C-labelled lactose and the effect of various conditions (pH, temperature and kind of support) on it and consequently on fermentation time and ethanol production was examined. The results showed that lac- tose uptake rate was correlated to fermentation rate and increased as temperature was increased up to 30 °C at pH 5.5. The same results have been recently noticed by using biocatalysts with Delignified Cel- lulosic Materials (DCM) and Gluten Pellets (GP), but fermentation time of about 7 h by kefir immobilized on DCM and BSG resulted to two fold lower than that on GP and MSR. The highest alcohol concentration was observed by MSR. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction It is well known that microorganisms cells take up carbohy- drates through their cell wall and it is obvious that this diffusion of carbohydrate molecules could play an important role on the fer- mentation rate. Therefore, research to examine cell carbohydrate uptake rate will visualize this phenomenon and will create the practical and theoretical background in supported productivity in bioprocesses. As recently has been reported, 14 C-labeled lactose was used for monitoring lactose uptake rate by free kefir cells and by immobilized ones in an attempt to confirm directly the positive effect of immobilized kefir on fermentation rate (Golfinopoulos et al., 2009, 2011, 2012). So, it was found that lactose uptake rate is strongly correlated to fermentation rate and increased during whey fermentation by kefir cells immobilized on Delignified Cellulosic Materials (DCM) and Gluten Pellets, (GP), in comparison with fermentation by free cells (FC). Whey is the main liquid by-product of the dairy activities, in which a large quantity of the lactose of the milk is removed (4.2–5%). But, it is usually discarded as a waste in the environ- ment, representing a grave pollutant. So, except of protein and whey lactose recovery processes, the improvement of whey lactose fermentation was necessary for the production of various bioprod- ucts, through biotechnological means. In that way the streams of whey could be used as an abundant and renewable potential raw material for microbial fermentations (Panesar et al., 2007). Over the last two decades, the natural mixed culture kefir was chosen for whey exploitation, due to its ability to ferment the lactose of whey mainly to ethanol and lactic acid (Athanasiadis et al., 2002; Panesar et al., 2010). In the present work two new biocatalysts prepared by immobilization of kefir on Brewer’s Spent Grains (BSG) or Malt Spent Rootlets (MSR) were used for whey fermentation. The BSG 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.12.131 ⇑ Corresponding author. Tel.: +30 2610 997124; fax: +30 2610 997118. E-mail address: m.soupioni@chemistry.upatras.gr (M. Soupioni). Bioresource Technology 145 (2013) 326–330 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech