Improvement of SCP production and BOD removal of whey with mixed yeast culture

Abstract

This research emphasizes on single cell protein (SCP) production and Biochemical Oxygen Demand (BOD) removal from whey with mixed yeast culture. For this purpose, 11 yeast strains were isolated from dairy products (M1-M11) and the strains were identified by morphological and physiological properties. These yeast strains were tested for their ability to reduce the BOD and to produce SCP from whey. Among these strains, K.lactis (M2) had the most SCP production from whey with the yield of 11.79 g/l. Ammonium sulphate as nitrogen source had an increasing effect on biomass yield. The mixed culture of the isolated yeast strains with Saccharomyces cerevisiae was used in order to increase the biomass yield and BOD removal. The highest biomass yield (22.38 g/l) and reduction of initial BOD from 30000 to 3450 mg/l were obtained with the mixed culture of K.lactis (M2) and S. cerevisiae.

Isolation and Characterization of Yeasts from Locally Available Foods

“…Average bio mass production was highest in Y66 yeast isolate obtained from a pudding sample and it was 11.7933 g/L in amount (Figure 4). A similar bio mass production has been reported in the research study conducted by Moeini et al, 2004 and the respected yeast was K. lactis. In addition to that, this literature reveals that the bio mass production can be raised further more by using mixed cultures of yeast species such as K. lactis, K.marxianus with S. cerevisiae and by the supplementation of the medium with a nitrogen source like ammonium sulphate.…”

“…Therefore, these two yeasts possess different modes of regulation which are responsible for their overall response for carbon sources and this may be the cause for major physiological differences they exhibit. Some Debaryomyces species, Candida species, Schizosaccharomyces pombe and Mrakia frigida also provide negative results for the lactose fermentation test (Moeini et al, 2004). In the studied yeast pool, 17%, which were lactose non-fermentative, can be predicted to be among these yeast species.…”

“…Literature reveals that S. cerevisiae is unable to grow and ferment in lactose medium when it is provided as the sole carbon source as it doesn't possess a lactose metabolizing system. ( (Moeini et al, 2004;Domingues et al, 2010). According to Domingues et al ( 2010), S. cerevisiae has majorly adapted to utilize glucose whereas K. lactis has adapted to lactose.…”

“…This was conducted by following the methodology used in the researches by Moeini et al, 2004 and. The carbon compounds tested were sucrose, glycerol, raffinose, D-maltose, Dmanitol and L-rhamnose.…”

“…The enzyme lactase, β−galactosidase which hydrolyze lactose into glucose and galactose, is produced by many microorganisms that utilize lactose as an energy source. Kluyveromyces species exhibit higher activity of this enzyme than other species (Moeini et al, 2004). Literature reveals that S. cerevisiae is unable to grow and ferment in lactose medium when it is provided as the sole carbon source as it doesn't possess a lactose metabolizing system.…”