Improving survival of probiotic bacteria using bacterial poly-γ-glutamic acid

Abstract

A major hurdle in producing a useful probiotic food product is bacterial survival during storage and ingestion. The aim of this study was to test the effect of γ-PGA immobilisation on the survival of probiotic bacteria when stored in acidic fruit juice. Fruit juices provide an alternative means of probiotic delivery, especially to lactose intolerant individuals. In addition, the survival of γ-PGA-immobilised cells in simulated gastric juice was also assessed. Bifidobacteria strains (Bifidobacteria longum, Bifidobacteria breve), immobilised on 2.5% γ-PGA, survived significantly better (P<0.05) in orange and pomegranate juice for 39 and 11 days respectively, compared to free cells. However, cells survived significantly better (P<0.05) when stored in orange juice compared to pomegranate juice. Moreover, both strains, when protected with 2.5% γ-PGA, survived in simulated gastric juice (pH2.0) with a marginal reduction (<0.47 log CFU/ml) or no significant reduction in viable cells after 4h, whereas free cells died within 2h. In conclusion, this research indicates that γ-PGA can be used to protect Bifidobacteria cells in fruit juice, and could also help improve the survival of cells as they pass through the harsh conditions of the gastrointestinal tract (GIT). Following our previous report on the use of γ-PGA as a cryoprotectant for probiotic bacteria, this research further suggests that γ-PGA could be used to improve probiotic survival during the various stages of preparation, storage and ingestion of probiotic cells.

Poly-γ-Glutamic Acid: Biodegradable Polymer for Potential Protection of Beneficial Viruses

“…This conformational change which is thought to allow phage to be effectively “wrapped up” or shielded by the now, filament-like polymer from acidic environments. This effect has already been investigated by similar study; Bhat and co-workers demonstrated that formulating probiotic bacteria with γ-PGA increases the survival rate remarkably in extreme acidic environment [9]. This biopolymer is able to form different engineering structures at different pH.…”

“…In addition, the polymer has been used in the protection and delivery of genetic materials and vaccines [1]. Recently, γ-PGA was shown to effectively protect probiotic bacteria from the effect of harsh environmental conditions for effective storage and enhanced delivery to their host [9]. However, the use of these polymers to protect active phage particles from harsh environmental conditions has previously not been studied.…”

“…It has also been used for protein and vaccine encapsulation, immobilization or adsorption for delivery to specific action sites [6,7,8]. Although no report of viral γ-PGA interaction was found in the literature, the encapsulation or immobilization of vaccines with this biodegradable polymers and its use in the protection of probiotic bacteria from harsh environmental conditions [7,8,9,10] suggest that γ-PGA can be used as an immobilization or encapsulating agent for bacteriophage to offer protection from harmful environmental conditions.…”

“…It is, therefore, necessary that methods be developed to protect phages from these environmental factors in order to improve their persistence in the environment for efficient storage and potential use as topical or environmental antibacterial agents. Previously, we have shown that the biodegradable polymer poly-γ-glutamic acid (γ-PGA) can be used to protect beneficial bacteria from various environmental factors during their various stages of preparation, storage and ingestion [9,10]. We therefore hypothesized that this polymer could also be applied in bacteriophage protection from harmful environmental factors.…”

Technological characterization of vaginal probiotic lactobacilli: resistance to osmotic stress and strains compatibility

“…) or the addition of poly‐Ƴ glutamic acid (Bhat et al . ). Different studies performed previously on the technological applications of lactobacilli in our group (not published) have shown some type of correlation between the metabolic ways that support their classification in the homo‐ or heterofermentative groups related mainly with their temperature resistance (Ludwig et al .…”