A novel consortium of Lactobacillus rhamnosus and Streptococcus thermophilus for increased access to functional fermented foods.

BACKGROUND: The lactic acid bacterium Lactobacillus rhamnosus GG is the most studied probiotic bacterium with proven health benefits upon oral intake, including the alleviation of diarrhea. The mission of the Yoba for Life foundation is to provide impoverished communities in Africa increased access to Lactobacillus rhamnosus GG under the name Lactobacillus rhamnosus yoba 2012, world's first generic probiotic strain. We have been able to overcome the strain's limitations to grow in food matrices like milk, by formulating a dried starter consortium with Streptococcus thermophilus that enables the propagation of both strains in milk and other food matrices. The affordable seed culture is used by people in resource-poor communities. RESULTS: We used S. thermophilus C106 as an adjuvant culture for the propagation of L. rhamnosus yoba 2012 in a variety of fermented foods up to concentrations, because of its endogenous proteolytic activity, ability to degrade lactose and other synergistic effects. Subsequently, L. rhamnosus could reach final titers of 1E+09 CFU ml(-1), which is sufficient to comply with the recommended daily dose for probiotics. The specific metabolic interactions between the two strains were derived from the full genome sequences of L. rhamnosus GG and S. thermophilus C106. The piliation of the L. rhamnosus yoba 2012, required for epithelial adhesion and inflammatory signaling in the human host, was stable during growth in milk for two rounds of fermentation. Sachets prepared with the two strains, yoba 2012 and C106, retained viability for at least 2 years. CONCLUSIONS: A stable dried seed culture has been developed which facilitates local and low-cost production of a wide range of fermented foods that subsequently act as delivery vehicles for beneficial bacteria to communities in east Africa.

Ligand promiscuity within the internal cavity of Epiphyas postvittana Takeout 1 protein.

Takeout proteins are found across a diverse range of insect species and are thought to be involved in important aspects of insect physiology and behavior. These proteins act as ligand carriers, but the nature of their endogenous ligands remains unknown. The crystal structure of Epiphyas postvittana Takeout 1 (EpTo1), the only structure for any Takeout protein to date, revealed an α/ß-wrap fold with a purely hydrophobic internal cavity of tubular shape. When recombinantly expressed in Escherichia coli, we previously showed that a surrogate ubiquinone-8 ligand binds within the internal cavity of EpTo1 with excellent shape complementarity. We have now expressed EpTo1 in an insect cell expression system devoid of ubiquinone-8, and solved its crystal structure at 2.2Å resolution. Using combined information from crystallography and mass spectrometry, we identify a mixture of fatty acid moieties, mostly myristic and palmitic acid, bound inside the EpTo1 cavity, mimicking the structure of the longer ubiquinone-8 compound. No significant alteration of the internal cavity was observed regardless of the bound ligands, ubiquinone-8 or fatty acids, suggesting that the internal cavity of EpTo1 forms a rigid scaffold that imposes strict structural constraints for selectivity and specificity of ligand(s) in vivo.