Increasing membrane protection in Lactobacillus plantarum cells overproducing small heat shock proteins

Mechanistic study of the differences in lactic acid bacteria resistance to freeze- or spray-drying and storage

Lactobacillus delbrueckii subsp. bulgaricus and Lactiplantibacillus plantarum are two lactic acid bacteria (LAB) widely used in the food industry. The objective of this work was to assess the resistance of these bacteria to freeze- and spray-drying and study the mechanisms involved in their loss of activity. The culturability and acidifying activity were measured to determine the specific acidifying activity, while membrane integrity was studied by flow cytometry. The glass transitions temperature and the water activity of the dried bacterial suspensions were also determined. Fourier transform infrared (FTIR) micro-spectroscopy was used to study the biochemical composition of cells in an aqueous environment. All experiments were performed after freezing, drying and storage at 4, 23 and 37 °C. The results showed that Lb. bulgaricus CFL1 was sensitive to osmotic, mechanical, and thermal stresses, while Lpb. plantarum WCFS1 tolerated better the first two types of stress but was more sensitive to thermal stress. Moreover, FTIR results suggested that the sensitivity of Lb. bulgaricus CFL1 to freeze-drying could be attributed to membrane and cell wall degradation, whereas changes in nucleic acids and proteins would be responsible of heat inactivation of both strains associated with spray-drying. According to the activation energy values (47-85 kJ/mol), the functionality loss during storage is a chemically limited reaction. Still, the physical properties of the glassy matrix played a fundamental role in the rates of loss of activity and showed that a glass transition temperature 40 °C above the storage temperature is needed to reach good preservation during storage. KEY POINTS: • Specific FTIR bands are proposed as markers of osmotic, mechanic and thermal stress • Lb. bulgaricus CFL1 was sensitive to all three stresses, Lpb. plantarum WCFS1 to thermal stress only • Activation energy revealed chemically limited reactions ruled the activity loss in storage.

Is the lipochaperone activity of sHSP a key to the stress response encoded in its primary sequence?

Several strategies have been put in place by organisms to adapt to their environment. One of these strategies is the production of stress proteins such as sHSPs, which have been widely described over the last 30 years for their role as molecular chaperones. Some sHSPs have, in addition, the particularity to exert a lipochaperone role by interacting with membrane lipids to maintain an optimal membrane fluidity. However, the mechanisms involved in this sHSP-lipid interaction remain poorly understood and described rather sporadically in the literature. This review gathers the information concerning the structure and function of these proteins available in the literature in order to highlight the mechanism involved in this interaction. In addition, analysis of primary sequence data of sHSPs available in database shows that sHSPs can interact with lipids via certain amino acid residues present on some β sheets of these proteins. These residues could have a key role in the structure and/or oligomerization dynamics of sHPSs, which is certainly essential for interaction with membrane lipids and consequently for maintaining optimal cell membrane fluidity.

Molecular chaperone function of three small heat-shock proteins from a model probiotic species

Small heat-shock proteins (sHSP) are ubiquitous ATP-independent chaperones that prevent irreversible aggregation of heat-damaged denaturing proteins. Lactiplantibacillus plantarum is a widespread Gram-positive bacterium with probiotic claims and vast potential for agro-food, biotechnological and biomedical applications. L. plantarum possesses a family of three sHSP, which were previously demonstrated to be involved in its stress tolerance mechanisms. Here, the three L. plantarum sHSP were heterologously expressed, purified and shown to have a chaperone activity in vitro, measuring their capacity to suppress protein aggregation, as assayed spectrophotometrically by light scattering. Their anti-aggregative capacity was found to be differently influenced by pH. Differences were also found relative to their holdase function and their capacity to modulate liposome membrane fluidity, suggesting interplays between them and indicating diversified activities. This is the first study assessing the chaperone action of sHSP from a probiotic model. The different roles of the three sHSP can increase L. plantarum's capabilities to survive the various types of stress characterising the diverse habitats of this highly adaptable species. Reported evidence supports the interest in L. plantarum as one of the model species for bacteria that have three different sHSP-encoding genes in their genomes.

Development of EPS rich herbal shampoo base fermented using Cyclea peltata leaf powder and Lactobacillus plantarum

BACKGROUND

Studies show that the extensive use of chemical shampoos has a negative impact on health. Given the recent trends, the use of herbal shampoos is gaining importance. Cyclea peltata is a common plant in Kerala's coastal region that has traditionally been used to aid in wound healing, allergy relief, and hair and scalp improvement. Greenly produced silver nanoparticles made from plant sources have a wide range of medical applications.

OBJECTIVE

The main objective is to optimize the base of the shampoo with better solid content by OFAT studies and characterize the silver nanoparticles synthesized using post optimized shampoo base.

METHOD

Cyclea peltata leaves were fermented with Lactobacillus plantarum for the shampoo formulation, substituting the chemical basis gelatin with an herbal fermented foundation. Silver nanoparticles combined with an herbal formulation should be as safe as herbal shampoo while also being as effective as chemical shampoo. Variation of concentration of Cyclea peltata leaf powder, variation of sucrose concentration, variation of concentration of yeast extract, variation of L.plantarum inoculum, variation of temperature, variation of agitation speed and variation of time were all studied using the OFAT (One Factor At a Time) method. Silver nanoparticles synthesized using post optimized shampoo bases were also characterised by particle size, zeta potential and FTIR analysis in order to better understand their properties.

RESULTS

The results clearly indicated that all the six factors had a significant effect on the growth and production of EPS. The pH considered for the shampoo base is above 5 so as to maintain the acidic mantle of the scalp. Green synthesized silver nanoparticles from post optimized shampoo base were obtained within 17^th hour of incubation, with single surface plasmon resonance at 420nm. Nanoparticles showed a peak at -11.6 mv of zeta potential which means that the particles are less agglomerative and stable. Similar groups were seen in ftir spectrum of fermented silver nanoparticles and the plant extract which confirmed the capping of nanoparticles with plant phytochemicals.

CONCLUSION

The study successfully prepared and characterized green synthesized silver nanoparticles from post optimized shampoo base and also optimized the shampoo base based on the EPS production. Characterization of the silver nanoparticles found that the nanoparticles synthesized were stable, less agglomerative and had several useful components present in it.