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Selected yeast (Kluyveromyces marxianus Y102 strain) and an acetic acid bacterium (Acetobacter aceti, DSM-G3508 strain) were used as inocula respectively in cheese whey for alcoholic and acetic fermentations. The experimental tests were carried out at both laboratory and pilot plant (20 L and 2000 L) levels. The data from the trials (working period 28 days) show increased ethanol production, increased acetic acid yield, and greater fermentation stability with biomass recycling (18.6 g L–1). Batch and fed-batch fermentation tests resulted in increased and standardized alcoholic fermentation, and allowed acetic acid recovery (average lactose consumption 56%, ethanol 6.7 g L–1 d–1 and acetic acid production 4.35 g L–1 d–1). The effects administration were then investigated on milk yield and composition, nutritional status of dairy cows and physical characteristics of total mixed ration (TMR). Twenty Holstein cows were divided into two groups; group C, receiving the traditional TMR, and group W, receiving the TMR plus 10 L wheynegar. The dietary treatment, lasted 35 days, did not affect milk yield and composition except for the urea content, significantly lowered in group W. The selection of coarse (<19 mm), medium (8-19 mm) and fine (<8 mm) dietary particles was not influenced by the wheynegar administration however a tendential lower selection against coarse particles was noted in W. The results highlight that microbial biotechnologies may significantly contribute to both the valorization of whey and the development of a stable nutrient recycling system as a ingredient in dairy cattle diet.
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