Several bacteria pathogens are responsible for plant diseases causing significant economic losses. The antibacterial activity of Dunaliella salina microalgae extracts were investigated in vitro and in vivo. First, biomass composition was chemically characterized and subjected to extraction using polar/non-polar solvents. The highest extraction yield was obtained using chloroform:methanol (1:1 v/v) equal to 170 mg g⁻¹ followed by ethanol (88 mg g⁻¹) and hexane (61 mg g⁻¹). In vitro examination of hexane extracts of Dunaliella salina demonstrated antibacterial activity against all tested bacteria. The hexane extract showed the highest amount of β-carotene with respect to the others, so it was selected for subsequent analyses. In vivo studies were also carried out using hexane extracts of D. salina against Pseudomonas syringae pv. tomato and Pectobacterium carotovorum subsp. carotovorum on young tomato plants and fruits of tomato and zucchini, respectively. The treated young tomato plants exhibited a reduction of 65.7% incidence and 77.0% severity of bacterial speck spot disease. Similarly, a reduction of soft rot symptoms was observed in treated tomato and zucchini fruits with a disease incidence of 5.3% and 12.6% with respect to 90.6% and 100%, respectively, for the positive control.

In this work, the performance of carotenoids extraction from Rhodotorula spp red yeast (strain ELP2022) using supercritical CO ₂ (CO ₂ -SFE) was compared to the traditional technique with organic solvent. For this purpose, the yeast was cultured in liquid medium, pre-treated with glass beads in 0.1 M NaHCO ₃ , and lyophilized. The extraction by CO ₂ -SFE was carried out using a bench scale equipment at 300, 400, and 500 bar whilst maintaining a constant CO ₂ flow rate (6 mL/min) and temperature (40 °C) resulting in an average extraction yields of 60.8 ± 1.1, 68.0 ± 1.4, and 67.6 ± 1.4 µg of total carotenoids per g of yeast (dry weight), respectively. Based on these results, three other experiments at 400 bar and a CO ₂ flow rate of 6 L/min were also performed. In specific, the temperature was increased up to 60 °C, and ethanol as a co-solvent was added at 40 and 60 °C. The results showed that the temperature does not have a significant effect on the extraction of carotenoids. On the contrary, the yields improved significantly in the presence of the co-solvent, and the percentage of recovery reached the mean values of 71.70% ± 1.4 and 73.86% ± 1.9 at 40 and 60 °C, respectively. Furthermore, from chromatographic analysis, four major peaks were observed and identified as torularhodin, torulene, γ-carotene, and β-carotene which represented about 53.4%, 6.4%, 8.3%, and 26.9% of total carotenoids, respectively. Therefore, these promising results show the potential of this green technique for obtaining high-value products, such as carotenoids, from yeasts and therefore avoiding the use of dangerous solvents.

Biomass-derived sugars are platform molecules that can be converted into a variety of final products. Non-food, lignocellulosic feedstocks, such as agroforest residues and low inputs, high yield crops, are attractive bioresources for the production of second-generation sugars. Biorefining schemes based on the use of versatile technologies that operate at mild conditions contribute to the sustainability of the bio-based products. The present work describes the conversion of giant reed (Arundo donax), a non-food crop, to ethanol and furfural (FA). A sulphuric-acid-catalyzed steam explosion was used for the biomass pretreatment and fractionation. A hybrid process was optimized for the hydrolysis and fermentation (HSSF) of C6 sugars at high gravity conditions consisting of a biomass pre-liquefaction followed by simultaneous saccharification and fermentation with a step-wise temperature program and multiple inoculations. Hemicellulose derived xylose was dehydrated to furfural on the solid acid catalyst in biphasic media irradiated by microwave energy. The results indicate that the optimized HSSF process produced ethanol titers in the range 43–51 g/L depending on the enzymatic dosage, about 13–21 g/L higher than unoptimized conditions. An optimal liquefaction time before saccharification and fermentation tests (SSF) was 10 h by using 34 filter paper unit (FPU)/g glucan of Cellic^® CTec3. C5 streams yielded 33.5% FA of the theoretical value after 10 min of microwave heating at 157 °C and a catalyst concentration of 14 meq per g of xylose.

The production of beneficial microorganisms is the first step to obtain a commercial-based product for application in agriculture. In this study, prickly pear (Opuntia ficus-indica) pruning waste was evaluated as a raw material for the production of large amounts of Plant Growth Promoting Microorganisms (PGPMs) reducing the number of generated wastes. Specifically, five PGPMs constituting a synthetic microbial consortium with complementing plant growth-promoting traits were grown on a laboratory scale and, subsequently, on a pilot scale using a 21-L bioreactor. Primarily, the physical-chemical characterization of the culture medium obtained from the juice of Opuntia cladodes was carried out, revealing the presence of sugars and organic acids with different molar ratios. Compared to conventional media, the waste medium did not show significant differences in bacterial growth efficiency. Instead, the survival rates of the bacteria grown in cladodes juice media, after air-drying on zeolite or freeze-drying, were significantly higher than those observed when they were grown in conventional media. The present work is the first conducted on a pilot-scale that maximizes the production of PGPMs in submerged fermentation using cladodes juice from Opuntia, reducing both economic and environmental impacts associated with the generation of wastes.