The plant growth-promoting potential of the mesophilic wood-rot mushroom Pleurotus pulmonarius

Flask and reactor scale production of plant growth regulators by Inonotus hispidus: optimization, immobilization and kinetic parameters

The aims of the presented study are to compare submerged, static, and solid-state fermentation in the production of gibberellic acid (GA3), indole acetic acid (IAA), and abscisic acid (ABA) by Inonotus hispidus, to optimize with a statistical approach, and to determine the kinetic parameters under flask and reactor conditions. The maximum concentrations of GA3, (2478.85 ± 68.53 mg/L), ABA, (273.26 ± 6.17 mg/L) and IAA (30.67 ± 0.19 mg/L) were obtained in submerged conditions. After optimization, these values reached 2998.85 ± 28.85, 339.47 ± 5.50, and 34.56 ± 0.25 mg/L, respectively. Immobilization of fungal cells on synthetic fiber, polyurethane foam, and alginate beads resulted in an increase in plant growth regulators (PGR) production by 5.53%- 5.79% under optimized conditions. At the reactor scale, a significant increase was observed for GA3 concentration, 5441.54 mg/L, which was 2.14 and 1.45 times higher than non-optimized and optimized conditions in the flask scale, respectively. The maximum values for ABA and IAA were 390.39 and 44.79 mg/L, respectively. Although the specific growth rate (µ) decreases relatively from non-optimized flask conditions to optimized reactor conditions, it was observed that the PGR amounts produced per liter medium (rp) and per gram biomass (Qp) increased significantly. This is the first report on the synthesis of PGR by Inonotus hispidus which could be crucial for sustainable agriculture.

Optimization and reactor-scale production of plant growth regulators by Pleurotus eryngii

The aims of the this study are to select the best cultivation type for plant growth regulator (PGR) production, to optimize PGR production with statistical experimental design, and to calculate bioprocess parameters and yield factors during PGR production by P. eryngii in flask and reactor scales. Submerged fermentation was the best cultivation type with 4438.67 ± 37.14, 436.95 ± 27.31, and 54.32 ± 3.21 mg/L of GA3, ABA, and IAA production values, respectively. The Plackett-Burman and Box-Behnken designs were used to determine effective culture parameters and interactive effects of the selected culture parameters on PGR production by Pleurotus eryngii under submerged fermentation. The statistical model is valid for predicting PGR production by P. eryngii. After these studies, maximum PGR production (7926.17 ± 334.09, 634.92 ± 12.15, and 55.41 ± 4.38 mg/L for GA3, ABA, and IAA, respectively) was reached on the 18th day of fermentation under optimized conditions. The optimum formula was 50 g/L fructose, 3 g/L NaNO3, and 1.5 g/L KH2PO4, 1 mg/L thiamine, incubation temperature 25 °C, initial medium pH 7.0, and an agitation speed of 150 rpm. The kinetics of PGR production was investigated in batch cultivation under 3-L stirred tank reactor conditions. Concentrations of GA3, ABA, and IAA of 10,545.00 ± 527.25, 872.32 ± 21.81, and 60.48 ± 3.48 mg/L were obtained at the reactor scale which were 4.1, 3.4, and 2.3 times higher than the initial screening values. The specific growth rate (µ), the volumetric (rp) and specific (Qp) PGR production rates, 486.11 mg/L/day and 107.43 mg/g biomass/day for GA3, confirmed the successful transfer of optimized conditions to the reactor scale. In the presented study, PGR production of P. eryngii is reported for the first time.

Bacillus amyloliquefaciens Increases the GABA in Rice Seed for Upregulation of Type I Collagen in the Skin

Biosynthesis of gamma-aminobutyric acid (GABA) can be achieved by naturally occurring microorganisms with the advantages of cost-effectiveness and safety. In this study, Bacillus amyloliquefaciens EH-9 strain (B. amyloliquefaciens EH-9), a soil bacterium, was used to promote the accumulation of GABA in germinated rice seed. Further, the topical application of supernatant from rice seed co-cultivated with soil B. amyloliquefaciens EH-9 can significantly increase the production of type I collagen (COL1) in the dorsal skin of mice. The knocking down of the GABA-A receptor (GABA_A) significantly reduced the production of COL1 in the NIH/3T3 cells and in the dorsal skin of mice. This result suggests that topical application of GABA can promote the biosynthesis of COL1 via its interaction with the GABA_A receptor in the dorsal skin of mice. In summary, our findings illustrate for the first time that soil B. amyloliquefaciens EH-9 elicits GABA production in germinated rice seed to upregulate the formation of COL1 in the dorsal skin of mice. This study is translational because the result shows a potential remedy for skin aging by stimulating COL1 synthesis using biosynthetic GABA associated with B. amyloliquefaciens EH-9.

Fungal pretreatment of lignocellulosic biomass for the production of plant hormone by Pichia fermentans under submerged conditions

The study was designed to evaluate the production of auxin by eukaryotic unicellular organism Pichia fermentans. Different media formulations were used for the production of indole-3-acetic acid (IAA) under broth and submerged conditions. Wheat straw-based production medium was formulated and optimized using statistical approach. The IAA production was significantly enhanced by nine folds, when the wheat straw was pretreated with Phanerochaete chrysosporium (150 µg/ml) as compared to untreated wheat straw (16.44 µg/ml). Partial purification of IAA was carried out by silica gel column chromatography and further confirmed by high-performance liquid chromatography. Exogenous application of crude and partially purified IAA positively influenced the Vigna radiata seedling growth. The number of lateral roots in the growing seedlings was significantly higher as compared to the control seeds. Thus, the present findings point towards an efficient production of plant hormone by yeast and white rot fungus using abundantly available wheat straw, which may lead to the development of cost-effective production of such metabolites and their further use in agricultural field to reduce the negative impact of chemical fertilizers.