Comparative Analysis of Three Types of Whey as Substrate for Fermentation by Kluyveromyces marxianus and its Influence on Isoamyl Acetate Synthesis

Abstract

Whey, the main byproduct in cheese manufacturing, has a high organic content, predominantly due to its lactose amount (45-60 g/L). There are three types of residues coming from cheese production: sweet whey (SW), acid whey (AW), and ricotta whey (RW). Each one presents physicochemical particularities that pose challenges when handled by small and medium enterprises, due to their costly treatment. An alternative to address this issue is the fermentation of such substrates to obtain value-added products.The goal of this research was to evaluate the fermentation with Kluyveromyces marxianus in the three types of raw whey for the production of isoamyl acetate, a compound responsible for the banana aroma. Several factors were analyzed: cellular growth, pH variations, reduction in lactose content, ethanol production, and isoamyl acetate generation. Cellular growth showed no signi cant differences between the three types of whey. Regarding pH, a decrease was recorded during the rst 48 hours down to an approximate value of 4.3, then it increased to reach values close to 7. In acid whey, 50.95 g/L of ethanol was obtained at 120 hours. On the other hand, the maximum observed production of isoamyl acetate was 160 mg/L. Finally, the maximum lactose consumption was observed in sweet whey, with an approximate percentage of 76% at 24 hours, higher than that of acid and ricotta whey, which ranged between 56 and 58%. HighlightsLactose consumption by Kluyveromyces marxianus is higher in sweet whey.Ethanol production by Kluyveromyces marxianus is higher in acid whey.The synthesis of isoamyl acetate by K. marxianus is not affected by the type of whey.Whey recovery can be used as a substrate to produce a value-added product.

Conversion of Sweet Whey to Bioethanol: A Bioremediation Alternative for Dairy Industry

“…Meanwhile, the simultaneous incorporation of precursors (L-Phe and (NH 4 ) 2 SO 4 ) managed to increase the BioEtOH concentration by 59.6% (F6). The L-Phe presence in the culture medium promoted the production of BioEtOH during the yeast's secondary metabolism, corresponding to the stationary growth phase [14]. Yeasts can transform amino acids into their respective fusel alcohols by the Ehrlich pathway.…”

“…Injector and detector temperatures were 250 • C and 300 • C, respectively. The furnace temperature was increased from 35 • C to 200 • C with a heating rate of 20 • C min −1 for 10 min [14]. Nitrogen was used as the carrying gas at a flow rate of 1 mL min −1 for all the samples.…”

“…Sufficient availability of nitrogen, phosphorus, traces, vitamins, and cofactors is important to secure the completion of the fermentation as fast as metabolically possible [7]. The production of BioEtOH with K. marxianus using whey as a substrate when permeated, pasteurized, and/or enriched was reported recently [14]. It has been reported that only 20% of the nitrogen source found in the sweet whey can be used for these kinds of yeast.…”