The Moringa oleifera leaf is an important source worldwide with a high nutritional value and functions in food and feed that may also treat a myriad of ailments but the leaf has low organoleptic properties and digestibility. To overcome this shortcoming, a novel Aspergillus niger was isolated from the Moringa leaf material. The fungal strain grows well on moist Moringa leaves and requires no additives. After performing a single factor test for temperature, moisture, inoculation size, and fermentation, the optimized condition was determined by using a response surface method, followed by a small-scale production test. The pleasant, sweet smelling aroma in the fermented leaves was then generated, supplementing than its native repulsive smell. The protein content and digestibility of the leaves increased by 23.4 % and 54.4 %, respectively; the direct-fed microbes reached up to 1.99 × 109 CFU per gram of fermented freeze-dried Moringa leaves. Digestive lignocellulolytic enzymes were substantially produced with 2.97 ± 0.24 U.g−1 of filter paper activity and 564.9 ± 37.4 U.g−1 of xylanase activity. Moreover, some functional components, such as flavonoids and γ-Aminobutyric acid content, were also significantly increased compared to that of the unfermented leaves. In conclusion, the feed quality and digestibility of Moringa oleifera leaves were greatly improved via solid-state fermentation by Aspergillus niger. Fermented Moringa oleifera can be used as a potentially high- quality feed alternative for the animal industry.
Nitrogen dioxide (NO2) at a high concentration is among the most common and harmful air pollutants. The present study aimed to explore the physiological responses of plants exposed to NO2. A total of 41 plants were classified into 13 functional groups according to the Angiosperm Phylogeny Group classification system. The plants were exposed to 6 μL/L NO2 in an open-top glass chamber. The physiological parameters (chlorophyll (Chl) content, peroxidase (POD) activity, and soluble protein and malondialdehyde (MDA) concentrations) and leaf mineral ion contents (nitrogen (N+), phosphorus (P+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), manganese (Mn2+), and zinc (Zn2+)) of 41 garden plants were measured. After NO2 exposure, the plants were subsequently transferred to a natural environment for a 30-d recovery to determine whether they could recover naturally and resume normal growth. The results showed that NO2 polluted the plants and that NO2 exposure affected leaf Chl contents in most functional groups. Increases in both POD activity and soluble protein and MDA concentrations as well as changes in mineral ion concentrations could act as signals for inducing defense responses. Furthermore, antioxidant status played an important role in plant protection against NO2-induced oxidative damage. NO2 poses a pollution risk to plant systems, and antioxidant status plays an important role in plant protection against NO2-induced oxidative damage. In conditions of strong air pollution, more evergreen plants may be considered in landscape design, particularly in seasonal regions. The results of this study may provide useful data for the selection of landscaping plants in NO2 polluted areas.
Foliar uptake of gaseous NO2 mainly occurs through the stomata and disrupts normal plant growth, but no detailed reports about the physiological responses of plants exposed to NO2 are available. In this study, to study leaf physicochemical responses, stomatal characteristics and chloroplast structure, we observed the leaves of Carpinus putoensis W.C.Cheng after exposure to NO2 (6 μL/L) for five time periods (0, 1, 6, 24, and 72 h) and after 30 days of recovery following NO2 exposure. Our results showed that short-duration exposure to a high concentration of NO2 had significant negative impacts (p < 0.05) on the chlorophyll content, photosynthesis and chloroplast-related physicochemical processes of C. putoensis leaves; with the exception of one hour of NO2 exposure, which was helpful for plant physiological responses. Moreover, NO2 exposure significantly increased the thickness of the palisade/spongy tissue and caused swelling of the thylakoids within the chloroplasts; this thylakoid swelling could be reversed by removing the pollutant from the air flow. Restoration of unpolluted air alleviated the toxic effects of NO2, as indicated by an increased chlorophyll content, net photosynthesis, and PSII maximum quantum yield. These results could support the development of a treatment for roadside trees that are exposed to NO2 as a major road pollutant.
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