A Novel Isolate of Bacillus cereus Promotes Growth in Tomato and Inhibits Clavibacter michiganensis Infection under Greenhouse Conditions.

The need to produce food in a sustainable way to counteract the effects of excessive use of agrochemicals opens the door to the generation of new technologies that are not based on fossil fuels and are less toxic to ecosystems. Plant growth-promoting bacteria (PGPB) could represent an alternative to chemical biofertilizers and pesticides offering protection for biotic and abiotic stresses. In this work, a bacterial isolate from roots of castor bean (Ricinus communis) was identified and named as Bacillus cereus strain "Amazcala" (B.c-A). This isolate displayed the ability to solubilize inorganic phosphate and produce gibberellic acid (GA3). Moreover, this bacterium provided significant increases in height, stem width, dry weight, and total chlorophyll content in tomato plants. Interestingly, B.c-A also significantly decreased the severity of bacterial canker disease on tomato caused by Clavibacter michiganensis (Cmm) in preventive disease assays under greenhouse conditions. Based on our results, B.c-A can be considered as PGPB and a useful tool in Cmm disease control on tomato plant under greenhouse conditions.

Comparative study of the production of extracellular ß-glucosidase by four different strains of Aspergillus using submerged fermentation.

Four strains of Aspergillus (Aspergillus niger CDBB-H-176, A. niger CDBB-H-175, A. niger ATCC 9642, and Aspergillus terreus CDBB-H-194) were used to produce extracellular ß-glucosidase. Using an orthogonal experimental design (L9), we optimized the parameters of culture medium to maximize the activity of ß-glucosidase. The optimal conditions (same for the four strains) were as follows: temperature, 30°C; pH, 6.0; orbital agitation, 200 rpm; concentration of sucrose, 0.5% (w/v). The most productive strain was A. niger CDBB-H-175, with a yield of 701.2 U/mL. In a second stage, we optimized (L18) the concentration of nutrients in the culture medium to determine whether this modification would increase the production of ß-glucosidase. The optimal conditions for A. niger CDBB-H-175 were as follows (%, w/v): NaNO3, 0.3; KCl, 0.3; KH2PO4, 0.15; NH4NO3, 0.1; NH4H2PO4, 0.1; MgSO4 · 7H2O, 0.05; yeast extract, 0.1. The production of ß-glucosidase under these conditions was 1207.9 U/mL. Enzymatic assays were used to characterize the enzyme; the optimum temperature and pH of ß-glucosidase produced by the four selected micro-organisms were found to be 65°C and 5.0, respectively. We determined the Michaelis-Menten constants (Km) only for A. niger CDBB-H-175 and CDBB-H-176; the values were 2.7 and 2.2 mM, respectively.

Antioxidant Capacity Analysis of Blackberry Extracts with Different Phytochemical Compositions and Optimization of their Ultrasound Assisted Extraction.

High antioxidant capacity molecules, such as anthocyanins, occur naturally in blackberry (Rubus fruticosus). In particular, 'Dasha' blackberry cultivar has scarcely been studied and, it is becoming economically more important in Mexico. In this study, several blackberry extraction conditions, conferred different amounts of detectable phytochemical groups that in turn were analysed with a new approach to investigate their influence on antioxidant capacity (AC). Additionally, a central composite design (CCD) was proposed to study effects of temperature and acidification on AC. Finally, an original approach was used to disclose interactions between the phytochemical content and the AC. Changes in size of the particles during extraction were reported for the first time, and the results showed evidence of swelling and dissolving of particles. UAE of fine and thick powders achieved similar efficiencies in contrast with maceration which showed large differences for the extraction of the tested sizes. CCD showed that low levels of acidification and high levels of temperature resulted in higher extraction of phytochemicals and AC. HPLC show that the main anthocyanidin may represent 88% of the total anthocyanins. Due to its relatively high abundance, cyanidyn-3-glucoside showed evidence of being the main cause of the changes in AC in 'Dasha' extracts. The use of mild conditions resulted in no degradation of anthocyanins and, therefore, there are no AC losses. A correlation plane was proposed to study synergisms of the extracts with other anthocyanins or phenolics.