Agro-food, petroleum, textile, and leather industries generate saline wastewater with a high content of organic pollutants such as aromatic hydrocarbons, phenols, nitroaromatics, and azo dyes. Halophilic microorganisms are of increasing interest in industrial waste treatment, due to their ability to degrade hazardous substances efficiently under high salt conditions. However, their full potential remains unexplored. The isolation and identification of halophilic and halotolerant microorganisms from geographically unrelated and geologically diverse hypersaline sites supports their application in bioremediation processes. Past investigations in this field have mainly focused on the elimination of polycyclic aromatic hydrocarbons and phenols, whereas few studies have investigated N-aromatic compounds, such as nitro-substituted compounds, amines, and azo dyes, in saline wastewater. Information regarding the growth conditions and degradation mechanisms of halophilic microorganisms is also limited. In this review, we discuss recent research on the removal of organic pollutants such as organic matter, in terms of chemical oxygen demand (COD), dyes, hydrocarbons, N-aliphatic and N-aromatic compounds, and phenols, in conditions of high salinity. In addition, some proposal pathways for the degradation of aromatic compounds are presented.

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Glycerol from biodiesel production was used as a substrate for valerate production in a 13.1-L anaerobic filter with an open microbiome. Ethanol at 15% of the influent chemical oxygen demand was supplemented as an additional electron donor source. The 114-day experimental period was divided in three phases which included initial adaptation phase, external sludge addition from a caproic acid producing reactor and valerate extraction using a pertraction system. Propionate (0.63-1.75 g COD L −1 day −1 ) and valerate (0.86-1.81 g COD L −1 day −1 ) were the main carboxylates formed throughout all operational phases. An increase in production rates of butyrate (0.26-0.31 g COD L −1 day −1 ), caproate (0.01-0.08 g COD L −1 day −1 ), and 1,3-propanediol (0.43-0.52 g COD L −1 day −1 ) was observed with addition of external caproic acid producing sludge rich in Clostridium members. In the operational phase with pertraction, a sudden decrease in 1,3-propanediol and concomitant increase in acid production were verified. Propionate and valerate reached higher production rates compared with the other two phases, suggesting that the pertraction system favored the oxidative pathway of glycerol fermentation. Valerate extraction reached a maximum of 30 g COD m −2 day −1 . The filter microbiome was highly diverse with Simpson index values close to 0.1 for the four sludge samples collected, and a concomitant increase in Megasphaera elsdenii and an increase in valerate production rates were observed. Hence, high valerate production and extraction rates through the carboxylate platform are a feasible alternative for crude glycerol valorization with a great potential for improvement in future research.

A new biosurfactant was obtained from a moderately halophilic bacterium identified as Bacillus tequilensis ZSB10 that was isolated from a saline water pond located in Tehuacan‐Cuicatlan valley, Mexico. A kinetic analysis of the bacterial growth of the ZSB10 strain showed a maximum growth at 24 h regardless of the initial pH (5, 7.4, and 9). The best results were found at pH = 7.4 in terms of bacterial growth, besides which the produced biosurfactant showed emulsifying and surfactant properties with an emulsification index (E24) and surface tension change (ΔST) of 54 ± 0% and 26 mN m−1, respectively. Extracted ZSB10 crude biosurfactant had a yield of 106 ± 6 mg L−1, an E24 = 58.4 ± 0.2%, and a ΔST = 26 mN m−1 with a critical micelle concentration (CMC) of 44.82 mg L−1. Also, its structure was characterized by MALDI‐TOF mass spectrometry as a surfactin, iturin A, and fengycin mixture whose main isoform was leu/ile‐7 C15 surfactin [M + Na]+. Finally, the ZSB10 crude biosurfactant showed antifungal activity against Helminthosporium sp., with a 79.3% growth inhibition and an IC50 of 1.37 mg per disc. Therefore, this biosurfactant could be used as biopesticide.

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