The role of milk fat globule size in modulating the composition of postbiotics produced by Bacillus subtilis and their effect on mammary epithelial cells

How Close Are We to the Production of Milk in Alternative Systems? The Fat Perspective

The growing demand for sustainable food systems has led to significant advancements in developing alternatives to animal-derived products. Dairy products are an important dietary source of proteins and fats; however, their production raises environmental concerns, including greenhouse gas emissions, extensive land and water usage, and biodiversity loss. Therefore, there is a need to develop sustainable, scalable solutions that will enable the production of quality replacements for animal-based foods with reduced environmental impacts. Recognizing that replacing animal-based products from a single source is currently not feasible; there is a need for high-quality sources of ingredients that can be combined to mimic the holistic product. In recent years, plant-based dairy alternatives have gained traction; however, their inability to replicate the sensorial experience of real milk-attributed largely to the unique composition and structure of milk fat-remains a key limitation. Cow's milk fat has distinctive characteristics, including a complex fatty acid profile, which is rich in short- and medium-chain saturated fatty acids with specific positional distribution. These characteristics of cow's milk play a role in delivering the aroma, texture, and mouthfeel of dairy products. Recent efforts have focused on leveraging precision fermentation and cellular agriculture to mimic these properties. This review explores the unique lipid composition of ruminant milk, the biosynthesis of milk fats, and the challenges of replicating these features in non-mammalian systems. Emphasis is placed on short-chain fatty acids and chain-termination mechanisms in fatty acid synthesis. By integrating insights from diverse biological systems, we aim to contribute to a deeper understanding of the complex processes related to milk fat synthesis.

The Stressogenic Impact of Bacterial Secretomes Is Modulated by the Size of the Milk Fat Globule Used as a Substrate

Milk fat globules (MFGs) are produced by mammary epithelial cells (MECs) and originate from intracellular lipid droplets with a wide size distribution. In the mammary gland and milk, bacteria can thrive on MFGs. Herein, we aimed to investigate whether the response of MECs to the bacterial secretome is dependent on the MFG size used as a substrate for the bacteria, and whether the response differs between pathogenic and commensal bacteria. We used secretomes from both Bacillus subtilis and E. coli. Proinflammatory gene expression in MECs was elevated by the bacteria secretomes from both bacteria sources, while higher expression was found in cells exposed to the secretome of bacteria grown on large MFGs. The secretome of B. subtilis reduced lipid droplet size in MECs. When the secretome originated from E. coli, lipid droplet size in MEC cytoplasm was elevated with a stronger response to the secretome from bacteria grown on large compared with small MFGs. These results indicate that MEC response to bacterial output is modulated by bacteria type and the size of MFGs used by the bacteria, which can modulate the stress response of the milk-producing cells, their lipid output, and consequently milk quality.

Microwave Dielectric Response of Bovine Milk as Pregnancy Detection Tool in Dairy Cows

The most reliable methods for pregnancy diagnosis in dairy herds include rectal palpation, ultrasound examination, and evaluation of plasma progesterone concentrations. However, these methods are expensive, labor-intensive, and invasive. Thus, there is a need to develop a practical, non-invasive, cost-effective method that can be implemented on the farm to detect pregnancy. This study suggests employing microwave dielectric spectroscopy (MDS, 0.5-40 GHz) as a method to evaluate reproduction events in dairy cows. The approach involves the integration of MDS data with information on milk solids to detect pregnancy and identify early embryonic loss in dairy cows. To test the ability to predict pregnancy according to these measurements, milk samples were collected from (i) pregnant and non-pregnant randomly selected cows, (ii) weekly from selected cows (n = 12) before insemination until a positive pregnancy test, and (iii) daily from selected cows (n = 10) prior to insemination until a positive pregnancy test. The results indicated that the dielectric strength of Δε and the relaxation time, τ, exhibited reduced variability in the case of a positive pregnancy diagnosis. Using principal component analysis (PCA), a clear distinction between pregnancy and nonpregnancy status was observed, with improved differentiation upon a higher sampling frequency. Additionally, a neural network machine learning technique was employed to develop a prediction algorithm with an accuracy of 73%. These findings demonstrate that MDS can be used to detect changes in milk upon pregnancy. The developed machine learning provides a broad classification that could be further enhanced with additional data.

Comparative lipidomics analysis of different-sized fat globules in sheep and cow milks

The effect of milk fat globule (MFG) size and species (sheep versus cow) on the lipid and protein compositions of sheep and cow milks was studied. The MFGs in raw cow and sheep milks were separated into six significantly different-sized (1.5-5.5 μm) groups by a gravity-based separation method, and their fatty acids, their lipidomes and the protein compositions of their MFG membranes were determined. The proportions of polar lipids increased but glycoproteins decreased with decreasing MFG size in both sheep milk and cow milk; the fatty acid composition showed few differences among the MFG groups. The average size of each MFG group was comparable between sheep milk and cow milk. Sheep milk contained higher proportions of short-chain fatty acids, medium-chain fatty acids and sphingomyelin than cow milk in all MFG groups. The proportion of glycoproteins was higher in cow MFG membrane than in sheep MFG membrane. The results suggested that the lipid and protein compositions were markedly species and size dependent.