Porungo cheese whey: a new substrate to produce ß-galactosidase.

The bioconversion of porungo cheese whey to produce ß-galactosidase in batch system was studied. The whey released after curd cutting and precipitation during porungo cheese production was collected in borosilicate flasks. Two strains of Kluyveromyces marxianus, CCT 4086 and CBS 6556, and whey supplementation with different nitrogen sources were evaluated. Different temperatures (30 °C and 37 °C) and pH values (5.0 to 7.0) were investigated to establish the best conditions for enzyme production. The highest enzymatic activity was obtained by K. marxianus CCT 4086 in porungo cheese whey supplemented with yeast extract (16.73 U mL-1). K. marxianus CCT 4086 produced superior ß-galactosidase activity when compared to CBS 6556 for all media tested (ranging from 11.69 to 14.40 U mL-1). Highest ß-galactosidase activity was reached under conditions of pH 7.0 and 30 °C using K. marxianus CCT 4086 in the better media composition. The lowest enzymatic activity was observed at 37 °C for all pH values tested (10.69 U mL-1 to 13.94 U mL-1) and a highest ß-galactosidase activity was reached in pH 7.0 for both two temperatures (11.42 to 15.93 U mL-1). Porungo cheese whey shows potential for industrial ß-galactosidase production by microbial fermentation.

Galactooligosaccharides: Physiological benefits, production strategies, and industrial application.

The concern for better life quality has been encouraging the bioprocess industries to develop technological strategies to obtain new biomolecules. Galactooligosaccharides (GOS) are an important class of food-grade oligosaccharides, being classified as non-digestible, and which present prebiotic potential, promoting better conditions of health and well-being. The main benefits include the selective stimulation of beneficial microorganisms, the decrease in the formation of toxic compounds, the increase in the absorption of minerals, improvement of an immune response, and a reduction in the severity of obesity and diabetes. This review approaches the recent methodologies and strategies to obtain GOS, their health benefits, purification, and technological properties for industrial application. Improvements in the process are continuously being investigated, with the technique of enzyme immobilization representing a potentially promising strategy. Sustainable GOS productions have been reported by the use of agro-industrial residues, such as cheese whey. Despite these advances, the main concern of the process consists in the low yield, which implies high investments in the purification of the bioproducts. Technological and nutritional approaches to the GOS application in different industrial sectors are also reported.

Dynamics of yeast immobilized-cell fluidized-bed bioreactors systems in ethanol fermentation from lactose-hydrolyzed whey and whey permeate.

We studied the dynamics of ethanol production on lactose-hydrolyzed whey (LHW) and lactose-hydrolyzed whey permeate (LHWP) in batch fluidized-bed bioreactors using single and co-cultures of immobilized cells of industrial strains of Saccharomyces cerevisiae and non-industrial strains of Kluyveromyces marxianus. Although the co-culture of S. cerevisiae CAT-1 and K. marxianus CCT 4086 produced two- to fourfold the ethanol productivity of single cultures of S. cerevisiae, the single cultures of the K. marxianus CCT 4086 produced the best results in both media (Y EtOH/S = 0.47-0.49 g g(-1) and Q P = 1.39-1.68 g L(-1) h(-1), in LHW and LHWP, respectively). Ethanol production on concentrated LHWP (180 g L(-1)) reached 79.1 g L(-1), with yields of 0.46 g g(-1) for K. marxianus CCT 4086 cultures. Repeated batches of fluidized-bed bioreactor on concentrated LHWP led to increased ethanol productivity, reaching 2.8 g L(-1) h(-1).

The modeling of ethanol production by Kluyveromyces marxianus using whey as substrate in continuous A-Stat bioreactors.

We investigated the kinetics of whey bioconversion into ethanol by Kluyveromyces marxianus in continuous bioreactors using the "accelerostat technique" (A-stat). Cultivations using free and Ca-alginate immobilized cells were evaluated using two different acceleration rates (a). The kinetic profiles of these systems were modeled using four different unstructured models, differing in the expressions for the specific growth (µ) and substrate consumption rates (r s), taking into account substrate limitation and product inhibition. Experimental data showed that the dilution rate (D) directly affected cell physiology and metabolism. The specific growth rate followed the dilution rate (µ≈D) for the lowest acceleration rate (a = 0.0015 h(-2)), condition in which the highest ethanol yield (0.52 g g(-1)) was obtained. The highest acceleration rate (a = 0.00667 h(-2)) led to a lower ethanol yield (0.40 g g(-1)) in the system where free cells were used, whereas with immobilized cells ethanol yields increased by 23 % (0.49 g g(-1)). Among the evaluated models, Monod and Levenspiel combined with Ghose and Tyagi models were found to be more appropriate for describing the kinetics of whey bioconversion into ethanol. These results may be useful in scaling up the process for ethanol production from whey.