Substrate contribution on free radical scavenging capacity of carotenoid extracts produced from Blakeslea trispora cultures

Engineering a photosynthetic bacteria-incorporated hydrogel for infected wound healing

Treating wounds with multidrug-resistant bacterial infections remains a huge and arduous challenge. In this work, we prepared a "live-drug"-encapsulated hydrogel dressing for the treatment of multidrug-resistant bacterial infections and full-thickness skin incision repair. Our live dressing was comprised of photosynthetic bacteria (PSB) and extracellular matrix (ECM) gel with photothermal, antibacterial and antioxidant properties, as well as good cytocompatibility and blood compatibility. More interestingly, live PSB could be regarded as not only photothermal agents but also as anti-inflammatory agents to promote wound healing owing to their antioxidant metabolites. In vitro and in vivo studies showed that the PSB hydrogel not only had a high killing rate against methicillin-resistant Staphylococcus aureus (MRSA) but it also accelerated collagen deposition and granulation tissue formation by promoting cell proliferation and migration, which significantly promoted skin tissue regeneration and wound healing. We believe that the large-scale production of PSB Gel-based therapeutic dressings has the advantages of easy use and promising clinical applications. STATEMENT OF SIGNIFICANCE: Rapid wound healing and the treatment of bacterial infections have always been the two biggest challenges in the field of wound care. We prepared a "live drug" dressing by encapsulating photosynthetic bacteria into an extracellular matrix hydrogel to sterilize the wound and promote wound healing. First, photosynthetic bacteria are not only a photothermal agent for photothermal wound sterilization, but also possess the anti-inflammatory capacity to enhance wound healing due to their antioxidant metabolites. Second, the extracellular matrix hydrogel is rich in a variety of growth factors and nutrients to promote cell migration and accelerate wound healing. Third, photosynthetic bacteria are not only green and non-toxic, but also can be obtained on a large scale, which facilitates manufacturing and clinical transformation.

Alleviation of tetrabromobisphenol A toxicity in soybean seedlings by Rhodopseudomonas palustris RP1n1

This study investigated the regulatory role of Rhodopseudomonas palustris RP11 in alleviating TBBPA-induced harmful effects in soybean seedlings. In this study, the characteristics of growth promotion by strain RP11 were studied by analysing 5-aminolevulinic acid (ALA) and indole-3-acetic acid (IAA) production, as well as phosphorus-solubilizing and potassium-solubilizing ability. In the pot culture conditions, we tested whether strain RP11 improved soybean seedlings tolerance against TBBPA by measuring the root length and physiological parameters of the seedlings treated with strain RP11 and different concentration of TBBPA (0, 5, 50, 100, and 1000 mg/kg) together. The results showed that strain RP11 secreted IAA and ALA, and solubilized phosphate and potassium. In pot trials, strain RP11 increased the root length, chlorophyll content, carotenoid content, soluble sugar and protein content of soybean seedlings treated with TBBPA, in comparison with the seedlings treated only with TBBPA. Furthermore, strain RP11 induced the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), decreased the malondialdehyde (MDA) content in soybean seedlings under TBBPA stress. It was concluded that strain RP11 alleviated TBBPA-induced harmful effects in soybean seedlings by the secretion of IAA and ALA, the accumulation of carotenoid, soluble sugar and soluble protein, and the induction of SOD, CAT and POD as well as nutrient adjustment of phosphorus and potassium levels.

The role of oxidative stress on carotene production by Blakeslea trispora in submerged fermentation

In aerobic metabolism, reactive oxygen species (ROS) are formed during the fermentation that can cause oxidative stress in microorganisms. Microbial cells possess both enzymatic and non-enzymatic defensive systems that may protect cells from oxidative damage. The antioxidant enzymes superoxide dismutase and catalase are the two key defensive enzymes to oxidative stress. The factors that induce oxidative stress in microorganisms include butylated hydroxytoluene (BHT), hydrogen peroxide, metal ions, dissolved oxygen tension, elevated temperature, menadione, junglone, paraquat, liquid paraffin, introduction to bioreactors of shake flask inocula and synthetic medium sterilized at initial pH 11.0. Carotenes are highly unsaturated isoprene derivatives. They are used as antioxidants and as coloring agents for food products. In fungi, carotenes are derived via the mevalonate biosynthesis pathway. The key genes in carotene biosynthesis are hmgR, ipi, isoA, carG, carRA and carB. Among microorganisms, Βlakeslea trispora is the main microorganism used for the production of carotenes on the industrial scale. Currently, the synthetic medium is considered the superior substrate for the production of carotenes in a pilot plant scale. The fermentation systems used for the production of carotenes include shake flasks, stirred tank fermentor, bubble column reactor and flat panel photobioreactor. This review summarizes the oxidative stresses in microorganisms and it is focused on the current status of carotene production by B. trispora including oxidative stress induced by BHT, enhanced dissolved oxygen levels, iron ions, liquid paraffin and synthetic medium sterilized at an initial pH 11.0. The oxidative stress induced by the above factors increases significantly the production of carotenes. However, to further reduce the cost of carotene production, new biotechnological methods with higher productivity still need to be explored.