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Rhizospheric and root-endophyte bacteria can stimulate plant growth through diverse biochemical mechanisms and pathways, particularly under biotic and abiotic stresses. For this reason, biotechnological trends on plant growth-promoting rhizobacteria (PGPR) application as biofertilizers, bioremediators, and stress alleviators are gaining increasing interest as ecofriendly strategies for sustainable agriculture management and soil restoration. The first steps needed to implement these technologies are isolation, screening, and characterization of PGPR that can be potentially applied as bioinoculants to alleviate biotic and/or abiotic stresses. Therefore, a complete and accurate methodological study and laboratory techniques are required to warrant the correct achievement of these steps. This review compiles and details the fundamentals, methods, and procedures of key protocols used in isolation and characterization of PGPR for plant stress alleviation.

A bacterial strain of Pseudomonas aeruginosa B0406 catalogued as pathogen opportunistic was capable to grow with waste cooking oil as only carbon source and produce a biosurfactant. Stability to pH (from 2 to 12), salinity (% NaCl from 0 to 20%) and temperature (from −20 °C up to 120 °C), of biosurfactants was evaluated using a response surface methodology. Biosurfactants reduced surface tension from 50 to 29 ± 1.0 mN/m. Pseudomonas aeruginosa B0406 showed a high biosurfactant yield 4.17 g/L ± 0.38. Biosurfactants stability applying a response surface methodology was observed with combining effect of pH, salinity and temperature. The three factors combined do not affect surface tension of biosurfactants produced by Pseudomonas aeruginosa B0406. Therefore, this biosurfactants are of interest for medical, cosmetic even environmental applications.

Supplementation of Selenium (Se) can improve the oxidative stability of meat products and retard metmyoglobin formation; so prolonging color. Effect of organic Se addition in the diets of sheep on meat stability; color and pH are limited and need to be studied. A study was conducted with eighteen Pelibuey female sheep at the finishing stage, and supplemented with organic Se-enriched Saccharomyces cerevisiae for sixty days to evaluate its effect on color and pH of Longissimus dorsi muscle. The research was conducted in a block randomized design considering three treatments; control (Se0) without the addition of yeast, or with 0.35 ppm of yeast (Se34) or with 0.60 ppm (Se59). Sheep were slaughtered at an average weight of 39.5 ± 4.41 kg. Meat color and pH were recorder in the cold carcass, 24 h after slaughtering, and during shelf life at 0, 4, 6 and 8 days after slaughtering under refrigeration at 4 °C. No significant differences were observed (P>0.05) for meat color and pH characteristics due to treatment. Decreased redness (a*) and Chroma (C*) values due to storage time were observed; however, the yellowness (b*) and angle Hue were increased. It could be concluded that supplementation of Se-enriched yeast in finishing sheep with 0.35 ppm and 0.60 ppm has no effect on meat color and pH characteristics.

The application of biosolids such as sewage sludge is a concern, because of the potential release of toxic metals after decomposition of the organic matter. The effect of application of sewage sludge (Sw) and compost (C) to the soil (S) on the Cu and Cd sorption, distribution and the quality of the dissolved organic matter (DOM) in the soil, was investigated under controlled conditions. Visible spectrophotometry, infrared spectroscopy, sorption isotherms (simple and competitive sorption systems), and sequential extraction methods were used. The E4/E6 (λ at 465 and 665 nm) ratio and the infrared spectra (IR) of DOM showed an aromatic behaviour in compost–soil (C–S); in contrast sewage sludge–soil (Sw–S) showed an aliphatic behaviour. Application of either Sw or C increased the Cu sorption capacity of soil. The Cd sorption decreased only in soil with a competitive metal system. The availability of Cu was low due to its occurrence in the acid soluble fraction (F3). The Cu concentration varied in accordance with the amounts of Cu added. The highest Cd concentration was found in the exchangeable fraction (F2). The Sw and C applications did not increase the Cd availability in the soil.