Adhesive Interactions Between Lactic Acid Bacteria and β-Lactoglobulin: Specificity and Impact on Bacterial Location in Whey Protein Isolate

Abstract

In the last decade, there has been an increasing interest in the potential health effects associated with the consumption of lactic acid bacteria (LAB) in foods. Some of these bacteria such as Lactobacillus rhamnosus GG (LGG) are known to adhere to milk components, which may impact their distribution and protection within dairy matrices and therefore is likely to modulate the efficiency of their delivery. However, the adhesive behavior of most LAB, as well as its effect on food structuration and on the final bacterial distribution within the food matrix remain very poorly studied. Using a recently developed high-throughput approach, we have screened a collection of 73 LAB strains for their adhesive behavior toward the major whey protein β-lactoglobulin. Adhesion was then studied by genomics in relation to common bacterial surface characteristics such as pili and adhesion-related domain containing proteins. Representative adhesive and non-adhesive strains have been studied in further depth through biophysical measurement using atomic force microscopy (AFM) and a relation with bacterial distribution in whey protein isolate (WPI) solution has been established. AFM measurements have revealed that bacterial adhesion to β-lactoglobulin is highly specific and cannot be predicted accurately using only genomic information. Non-adhesive strains were found to remain homogeneously distributed in solution whereas adhesive strains gathered in flocs. These findings show that several LAB strains are able to adhere to β-lactoglobulin, whereas this had only been previously observed on LGG. We also show that these adhesive interactions present similar characteristics and are likely to impact bacterial location and distribution in dairy matrices containing β-lactoglobulin. This may help with designing more efficient dairy food matrices for optimized LAB delivery.

Impact of Lacticaseibacillus rhamnosus GG on the Emulsion Stability of Raw Milk

“…In raw milk, the LGG WT strain appears to be more aggregated than LGG Δ spaCBA, which was regularly distributed as single chains within the matrix. The cell aggregation of highly adhesive strains was previously observed for LGG and other lactic acid bacteria incorporated in whey solutions while they were homogenously distributed in a culture medium [ 30 ]. Overall, the CLSM results indicate that microbial surface properties may affect the location of the cells within the matrix.…”

“…On the other hand, the bacterial aggregates might be mediated by the interaction of LGG WT, through SpaCBA, with β-lactoglobulin [ 31 ]. Indeed, LGG WT was found to be randomly distributed when analysed in culture medium while aggregated in whey protein solution [ 30 ]. Lactobacillus aquaticus , an LAB without predicted SpaCBA pili or a pili-like structure, exhibited a similar behaviour [ 30 ].…”

“…Indeed, LGG WT was found to be randomly distributed when analysed in culture medium while aggregated in whey protein solution [ 30 ]. Lactobacillus aquaticus , an LAB without predicted SpaCBA pili or a pili-like structure, exhibited a similar behaviour [ 30 ]. These observations confirm the key role of SpaCBA pili but preclude their exclusivity.…”

“…The addition of LGG Δ spaCBA to raw milk led to a major effect. The bacterial aggregates were no longer observed, and bacteria were homogeneously distributed within the matrix, such as in culture media or whey protein solution [ 30 ]. Due to their dispersion and motion in raw milk, LGG Δ spaCBA bacteria were able to affect creaming by forming a barrier between fat globules, thereby delaying flocculation.…”

Atomic force microscopy of food assembly: Structural and mechanical insights at the nanoscale and potential opportunities from other fields

“…With this approach, the colloidal probe technique (section 4.3) was used to measure the adhesion between a BSA-coated probe and lysozyme or dextran deposited on a substrate (Singh et al, 2015;Xu & Logan, 2005) or between a BSA-coated probe and different ultrafiltration membranes (Richard Bowen, Hilal, Lovitt, & Wright, 1999). Colloidal probes coated with milk proteins, milk fat globule membrane fragments or mucin have allowed significant advances in quantifying their adhesion onto probiotic bacteria surfaces (Burgain et al, 2015(Burgain et al, , 2014aGomand et al, 2019;Guerin et al, 2016) or on cell surfaces (Guerin et al, 2018). These various studies by the LIBio (Nancy, France) has gone into the detail of evaluating adhesion between milk protein or milk fat globule membrane and various motifs of the bacterial surface such as pili or exopolysaccharide.…”