Native Mesorhizobium strains improve yield and nutrient composition of the common bird's-foot trefoil grown in an acid soil

10 Pág.Acid soils occupy more than 3.95 billion ha of the world soils, and finding an adequate solution for the limitation of crop production on these soils is indispensable. Using highly effective rhizobia tolerant to low pH enables successful nodulation and quality crop production of legumes in acid soils. In this study, isolation and characterization of native rhizobia associated with root nodules of bird's-foot trefoil (Lotus corniculatus L.) from Serbia were conducted. Their effects on the plant yield and nutrient composition of bird's-foot trefoil grown in an acid soil (pH 5.4), in a pot experiment were evaluated. Out of 72 strains isolated, 40 could nodulate bird's-foot trefoil when reinoculated in the test tubes under gnotobiotic conditions, and 23 isolates showed high nitrogen-fixing efficiency. Overall, all isolates could grow well in medium with a pH between 4.5 and 8. Indole-3-acetic acid (IAA) production was detected in all nodulating isolates and 24 could solubilize inorganic phosphates. The identification of selected isolates showed that all belong to Mesorhizobium genus (M. tianshanense, M. erdmanii, M. cantuariense, M. loti, M. jarvisii and M. caraganae). Four acid-tolerant isolates (1M12, 631oz, U1C, and 754) with high nitrogen-fixing efficiency in vitro and particular PGP traits were selected for the pot experiment with acid soil. All applied bacterial treatments (except 1M12) increased the shoot dry weight of bird's-foot trefoil plants (up to 50%), compared to the control. In addition, N uptake and N% were increased up to 20% by inoculation. All applied treatments influenced the concentrations and improved uptake of macro (P, K, Ca, and Mg) and micronutrients (Cu, Fe, Mn, Ni, Zn, and B) in the plant material. The obtained results indicated that satisfactory yield and mineral composition of L. corniculatus in acid soils could be achieved by inoculation with selected Mesorhizobium strains.This research was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, under the contract numbers 451-03-9/2021-14/200011 and 451-03-9/2021-14/200178.Peer reviewe

From Agricultural Waste to Biofuel: Enzymatic Potential of a Bacterial Isolate Streptomyces fulvissimus CKS7 for Bioethanol Production

Purpose To avoid a negative environmental and economic impact of agricultural wastes, and following the principles of circular economy, the reuse of agricultural wastes is necessary. For this purpose, isolation of novel microorganisms with potential biotechnological application is recommended. The current researches in bioethanol production are aimed to reduce the production costs using low-cost substrates and in-house produced enzymes by novel isolated microorganisms. In line with this, in this study valorization of these agricultural by-products by novel isolate S. fulvissimus CKS7 to biotechnological value added products was done. Methods Standard microbiological methods were used for the isolation and characterization of strain. Enzymes activities were determinated using DNS method while, the ethanol concentration was determined based on the density of the alcohol distillate at 20 degrees C. Results The maximal enzymatic activities for amylase, cellulases (carboxymethyl cellulase and Avicelase), pectinase and xylanase were achieved using rye bran as a waste substrate for CKS7 growth. Obtained crude bacterial enzymes were used for enzymatic hydrolysis of lignocellulosic materials including horsetail waste, yellow gentian waste, corn stover, cotton material and corona pre-treated cotton material. The maximum yield of reducing sugars was obtained on horsetail waste and corona pre-treated cotton material. Waste brewer's yeast Saccharomyces cerevisiae was successfully used for the production of bioethanol using horsetail waste hydrolysate and corona pre-treated cotton material hydrolysate. Conclusion The obtained results showed that bacterial strain CKS7 has a significant, still unexplored enzymatic potential that could be used to achieve a cleaner, environmental friendly and economically acceptable biofuel production. [GRAPHICS]