Assessment of different Bacillus coagulans strains for l-lactic acid production from defined media and gardening hydrolysates: Effect of lignocellulosic inhibitors

Cellulose valorisation has been successfully addressed for years. However, the use of hemicellulosic hydrolysates is limited due to the presence of C5-sugars and inhibitors formed during pretreatment. Bacillus coagulans is one of the few bacteria able to utilize both C6- and C5-sugars to produce l-lactic acid, but its susceptibility to the lignocellulosic inhibitors needs further investigation. For such a purpose, the tolerance of different B. coagulans strains to increasing concentrations of inhibitors is studied. The isolated A162 strain reached the highest l-lactic acid productivity in all cases (up to 2.4 g L^-1  h^-1), even in presence of 5 g L^-1 of furans and phenols. Remarkably, most of furans and phenolic aldehydes were removed from defined media and hemicellulosic gardening hydrolysate after fermentation with A162. Considering the high productivities and the biodetoxifying effect attained, A162 could be pointed out as a great candidate for valorisation of mixed sugars from hemicellulosic hydrolysates with high inhibitors concentration, promoting the implementation of lignocellulosic biorefineries.

Survival of probiotic bacteria in the presence of food grade nanoparticles from chocolates: an in vitro and in vivo study

The use of probiotics to treat gastrointestinal diseases such as diarrhea especially in children is becoming increasingly popular. Besides, the use of nanomaterials in food products is increasing rapidly especially in candies and chocolates. How these nanomaterials influence probiotic bacteria and their activity remains unexplored. Therefore, nanomaterials from commercial chocolate were purified and characterized by using SEM-EDS and XRD. The tested chocolate contained nano-TiO₂ with an average size of ~ 40 nm. The influence of the extracted TiO₂ on a commercial probiotic formulation usually used to treat diarrhea in children was studied. The probiotic formulation contained Bacillus coagulans, Enterococcus faecalis, and Enterococcus faecium as evident from 16S rRNA gene sequences and polyphasic characterization. Isolated bacteria exhibited known probiotic activities like biofilm formation, acid production, growth at 6% salt, and antibiotic resistance. TiO₂ from chocolates inhibited the growth and activity of the probiotic formulation over a concentration range of 125-500μg/ml in vitro. Based on results, it is estimated that 20 g of such chocolate contains enough TiO₂ to disturb the gut microbial community of children aged 2-8 years with a stomach capacity of ~ 0.5-0.9 l. The in vivo study on white albino mice shows the same response but with a higher dose. The results obtained by plate counts, MTT assay, live/dead staining, and qPCR suggest that TiO₂ from chocolates inhibits the growth and viability of probiotic bacteria in mice gut even at a concentration of 50-100 μg/day/mice. Therefore, TiO₂ in chocolate discourages survival of probiotic bacteria in the human gut.

Layer-by-Layer Encapsulation of Probiotics for Delivery to the Microbiome

The gastrointestinal (GI) microbiome is widely investigated for its role in many diseases. However, technologies designed for microbiome delivery are lacking. Here, a layer-by-layer (LbL) approach is reported for probiotic encapsulation to protect probiotics against GI tract insults and improve their adhesion and growth on the intestines. These advantages translate to significantly enhanced survival of LbL-probiotics in vivo.