The two most important bacterial phyla in the gastrointestinal tract, Firmicutes and Bacteroidetes, have gained much attention in recent years. The Firmicutes/Bacteroidetes (F/B) ratio is widely accepted to have an important influence in maintaining normal intestinal homeostasis. Increased or decreased F/B ratio is regarded as dysbiosis, whereby the former is usually observed with obesity, and the latter with inflammatory bowel disease (IBD). Probiotics as live microorganisms can confer health benefits to the host when administered in adequate amounts. There is considerable evidence of their nutritional and immunosuppressive properties including reports that elucidate the association of probiotics with the F/B ratio, obesity, and IBD. Orally administered probiotics can contribute to the restoration of dysbiotic microbiota and to the prevention of obesity or IBD. However, as the effects of different probiotics on the F/B ratio differ, selecting the appropriate species or mixture is crucial. The most commonly tested probiotics for modifying the F/B ratio and treating obesity and IBD are from the genus Lactobacillus. In this paper, we review the effects of probiotics on the F/B ratio that lead to weight loss or immunosuppression.

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Almost all of the 200 or so approved biopharmaceuticals have been produced in one of three host systems: the bacterium Escherichia coli, yeasts (Saccharomyces cerevisiae, Pichia pastoris) and mammalian cells. We describe the most widely used methods for the expression of recombinant proteins in the cytoplasm or periplasm of E. coli, as well as strategies for secreting the product to the growth medium. Recombinant expression in E. coli influences the cell physiology and triggers a stress response, which has to be considered in process development. Increased expression of a functional protein can be achieved by optimizing the gene, plasmid, host cell, and fermentation process. Relevant properties of two yeast expression systems, S. cerevisiae and P. pastoris, are summarized. Optimization of expression in S. cerevisiae has focused mainly on increasing the secretion, which is otherwise limiting. P. pastoris was recently approved as a host for biopharmaceutical production for the first time. It enables high-level protein production and secretion. Additionally, genetic engineering has resulted in its ability to produce recombinant proteins with humanized glycosylation patterns. Several mammalian cell lines of either rodent or human origin are also used in biopharmaceutical production. Optimization of their expression has focused on clonal selection, interference with epigenetic factors and genetic engineering. Systemic optimization approaches are applied to all cell expression systems. They feature parallel high-throughput techniques, such as DNA microarray, next-generation sequencing and proteomics, and enable simultaneous monitoring of multiple parameters. Systemic approaches, together with technological advances such as disposable bioreactors and microbioreactors, are expected to lead to increased quality and quantity of biopharmaceuticals, as well as to reduced product development times.

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Electrospinning is a technique that uses polymer solutions and strong electric fields to produce nano-sized fibers that have wide-ranging applications. We present here an overview of the use of electrospinning to incorporate biological products into nanofibers, including microorganisms, cells, proteins, and nucleic acids. Although the conditions used during electrospinning limit the already problematic viability/stability of such biological products, their effective incorporation into nanofibers has been shown to be feasible. Synthetic polymers have been more frequently applied to make nanofibers than natural polymers. Polymer blends are commonly used to achieve favorable physical properties of nanofibers. The majority of nanofibers that contain biological product have been designed for therapeutic applications. The incorporation of these biological products into nanofibers can promote their stability or viability, and also allow their delivery to a desired tissue or organ. Other applications include plant protection in agriculture, fermentation in the food industry, biocatalytic environmental remediation, and biosensing. Live cells that have been incorporated into nanofibers include bacteria and fungi. Nanofibers have served as scaffolds for stem cells seeded on a surface, to enable their delivery and application in tissue regeneration and wound healing. Viruses incorporated into nanofibers have been used in gene delivery, as well as in therapies against bacterial infections and cancers. Proteins (hormones, growth factors, and enzymes) and nucleic acids (DNA and RNA) have been incorporated into nanofibers, mainly to treat diseases and enhance their stability. To summarize, incorporation of biological products into nanofibers has numerous advantages, such as providing protection and facilitating controlled delivery from a solid form with a large surface area. Future studies should address the challenge of transferring nanofibers with biological products into practical and industrial use.

BackgroundIn vivo imaging of orally administered lactic acid bacteria (LAB) and commensal bacteria in mice is shown to provide information on the spatial and temporal distribution of bacteria in the gastrointestinal tract. The bacteria can be detected and monitored using bioluminescence or near-infrared fluorescence.ResultsFluorescence imaging of bacteria was established by expressing the infrared fluorescent protein IRFP713 in Lactococcus lactis, Lactobacillus plantarum and Escherichia coli. All three bacterial species were monitored in live mice and no major differences in transit time were observed. Bacteria passed through the stomach and small intestine in 1 h and the majority were secreted from the large intestine after 6–8 h. Intestinal localization of bacteria was confirmed by imaging the isolated intestines and culturing the intestinal content. The use of fluorescence tomography for spatial localization of fluorescent bacteria has been established. The expression of an additional infrared fluorescent protein IRFP682 enabled concomitant detection of two bacterial populations in live mice.ConclusionsThe present work provides a methodological basis for future studies of probiotic and theranostic actions of LAB in mouse disease models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-015-0376-4) contains supplementary material, which is available to authorized users.

Lactic acid bacteria (LAB) have a long history of use in the food industry. Some species are part of the normal human microbiota and have beneficial properties for human health. Their long-standing use and considerable biotechnological potential have led to the development of various systems for their engineering. Together with novel approaches such as CRISPR-Cas, the established systems for engineering now allow significant improvements to LAB strains. Nevertheless, genetically modified LAB (GM-LAB) still encounter disapproval and are under extensive regulatory requirements. This review presents data on the prospects for LAB to obtain ‘generally recognized as safe’ (GRAS) status. Genetic modification of LAB is discussed, together with problems that can arise from their engineering, including their dissemination into the environment and the spread of antibiotic resistance markers. Possible solutions that would allow the use of GM-LAB are described, such as biocontainment, alternative selection markers, and use of homologous DNA. The use of GM-LAB as cell factories in closed systems that prevent their environmental release is the least problematic aspect, and this is also discussed.