ARTICLE | doi:10.20944/preprints202107.0682.v1
Subject: Engineering, Automotive Engineering Keywords: fed-batch fermentation; kefir grains; probiotic culture; whey
Online: 30 July 2021 (09:12:13 CEST)
Nowadays, probiotics has been proposed for substituting antibiotics in animal feed, since the European Union (EU) banned the latter compounds in 2006 to avoid their serious side effects on human health. Therefore, this work aimed to produce a probiotic product by fed-fermentation of whey with kefir grains for use in animal feed. The whey was fermented with a combination of kefir grains AGK1 and the free biomass present in whole milk fermented milk used to activate these kefir grains. The probiotic culture obtained was characterized with high levels of biomass, total viability and antibacterial activity. Some probiotic properties of the probiotic culture were investigated in vitro, including its survival at low pH values, under simulated gastrointestinal conditions, after freezing in skim milk at − 20 ºC, and in the commercial feed during storage at room temperature. The viable cells of lactic and acetic acid bacteria and yeasts exhibited higher tolerance to acidic pH and simulated gastrointestinal conditions when the cells were protected with skim milk and piglet feed, compared with washed cells. The results indicated the feasibility of producing a probiotic product at a low cost with a potential application in animal feed.
ARTICLE | doi:10.20944/preprints202102.0311.v1
Subject: Life Sciences, Biochemistry Keywords: nisin; antibacterial molecule; batch fermentation; four-dimensional LV equation; Lactococcus lactis.
Online: 12 February 2021 (15:12:52 CET)
Nisin, an antibacterial compound produced by Lactococcus lactis strains, has been approved by the US Food and Drug Administration to be used as a safe food additive to control the growth of undesirable pathogenic bacteria. Nisin is commonly described as a pH-dependent primary metabolite, since its production depends on growth and culture pH evolution. However, the relationship between bacteriocin synthesis and the consumption of the limiting nutrient has not been described until now. Therefore, this study aimed to develop a competitive four-dimensional Lotka Volterra-like equation to describe the relationships between culture pH, limiting nutrient (total nitrogen: TN) consumption and production of biomass (X) and nisin (BT) in four series of batch fermentation with L. lactis CECT 539 in diluted whey (DW)-based media. The developed four-dimensional LV-like equation (with a unique set of parameters) could not be used to describe all cultures belonging to each fermentation series. However, the four-dimensional LV-like equation described accurately each individual culture, providing a good description of the relationships between pH, TN, X and BT, higher values for R2 and F-ratios, lower values (< 10%) for the mean relative percentage deviation modulus, with bias and accuracy factor values approximately equal to one.