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Abstract Background Discarded potato is the most abundant potato waste and represents a worldwide disposal problem to the potato industry. This agricultural waste contains valuable nutrients that could be used as substrate to obtain diverse high value-added microbial products, such as biopigments. The aim of this work was to evaluate the use of discarded potato as a sole substrate source for producing blue pigments by Streptomyces lydicus PM7 through submerged fermentation. Results Initially, the traditional culture medium ISP2 was established as suitable for inoculum preparation, as it allowed high growth rates and consumption of ~ 75% reducing sugar, leading to 1.3 g L−1 dry biomass at 72 h of incubation. The formulated discarded potato broth (DPB) medium was evaluated together with five other traditional liquid culture media (potato dextrose broth, ISP2, ISP3, ISP4, and ISP5) for producing blue pigments by S. lydicus PM7. The highest blue pigment production was obtained by using DPB medium, reaching ~ 0.97 g L−1, followed by ISP5 (~ 0.36 g L−1). In terms of evaluating the concentration of discarded potato powder, the highest concentration of blue pigments was obtained with 16 g L−1, compared to concentrations of 4, 8, and 32 g L−1. In general, a notable increase in total proteins (~ 14 g L−1 in biomass; ~ 8 g L−1 in medium) and reducing sugars (~ 5 g L−1) on the fifth day of DPB fermentation was observed, at which time the production of blue pigments began. These data proved that S. lydicus PM7 is able to degrade potato wastes during submerged fermentation and to direct metabolism towards the formation of biopigments. Chromatographic analysis revealed that the main blue pigment produced by new strain in this complex medium is actinorhodin. Conclusions Discarded potato favored the production of blue pigments by S. lydicus PM7 under submerged fermentation, leading to final product concentration almost three times higher than others traditional Streptomyces culture media. To the best of our knowledge, this is the first report on the production of actinorhodin by the specie S. lydicus, as well as on this pigment synthesis based on an agricultural waste as a sole nutrient source for fermentation process. The findings showed that potato waste could be a potential byproduct for replacement of commercial culture media using for this same purpose. Graphical Abstract

The fungicide iprodione (IPR) (3-(3,5-dichlorophenyl) N-isopropyl-2,4-dioxoimidazolidine-1-carboxamide) is a highly toxic compound. Although IPR has been restricted, it is still being applied in many places around the world, constituting an environmental risk. The biodegradation of IPR is an attractive option for reducing its residues. In this study, we isolated thirteen IPR-tolerant bacteria from a biopurification system designed to treat pesticides. A study of biodegradation using different strains was comparatively evaluated, and the best degradation rate of IPR was presented by Achromobacter sp. C1 with a half-life (T1/2) of 9 days. Based on a nano-LC-MS/MS analysis for the strains, proteins solely expressed in the IPR treatment were identified by highlighting the strain Achromobacter sp. C1, with 445 proteins primarily involved in the biosynthesis of secondary metabolites and microbial metabolism in diverse environments. Differentially expressed protein amidases were involved in six metabolic pathways. Interestingly, formamidase was inhibited while other cyclases, i.e., amidase and mandelamide hydrolase, were overexpressed, thereby minimizing the effect of IPR on the metabolism of strain C1. The dynamic changes in the protein profiles of bacteria that degrade IPR have been poorly studied; therefore, our results offer new insight into the metabolism of IPR-degrading microorganisms, with special attention paid to amidases.

Biosurfactant-producing bacteria can be found in contaminated environments such as biopurification systems (BPS) for pesticide treatments. A total of 18 isolates were screened to determine their ability to produce extracellular biosurfactants, using olive oil as the main carbon source. Out of the eighteen isolates, two strains (C11 and C27) were selected for biosurfactant production. The emulsification activities of the C11 and C27 strains using sunflower oil was 58.4 and 53.7%, respectively, and 46.6 and 48.0% using olive oil. Using molecular techniques and MALDI-TOF, the strains were identified as Bacillus amyloliquefaciens (C11) and Streptomyces lavendulae (C27). The submerged cultivation of the two selected strains was carried out in a 1 L stirred-tank bioreactor. The maximum biosurfactant production, indicated by the lowest surface tension measurement, was similar (46 and 45 mN/m) for both strains, independent of the fact that the biomass of the B. amyloliquefaciens C11 strain was 50% lower than the biomass of the S. lavendulae C27 strain. The partially purified biosurfactants produced by B. amyloliquefaciens C11 and S. lavendulae C27 were characterized as a lipopeptide and a glycolipid, respectively. These outcomes highlight the potential of the selected biosurfactant-producing microorganisms for improving pesticides’ bioavailability and therefore the degradational efficacy of BPS.

The extreme weather conditions in the Antarctic have exerted selective pressures favoring differential features in bacteria to survive this untapped environment (i.e., antibiotic molecules). Notably, higher chances of antibiotic discovery from extremophiles have been proposed recently. Althoughnew organic and environmentally friendly sources for helping in the control of plant pathogenic fungi are necessary, the information about anti-phytopathogenic applications of extremophile microorganisms from untapped environments is limited. In this study, we determined the antifungal effect of actinobacterial strains isolated from Antarctic soils and sediments. Co-culture inhibition assays and Minimum Inhibitory Concentration (MIC) determination revealed that all Antarctic strains (x28) can inhibit the growth of at least one phytopathogenic fungi including Fusarium oxysporum,Rhizoctonia solani,Botrytissp. and Phytophthora infestans. Additionally, new novel antagonistic relationships are reported. Our work establishes a precedent on Antarctic actinobacteria strains with the capacity to produce antifungal compounds, and its potential for developing new fungicides or biocontrol agents solving current agriculture problems.

In this study, we selected and characterized different pesticide-tolerant bacteria isolated from a biomixture of a biopurification system that had received continuous applications of a pesticides mixture. The amplicon analysis of biomixture reported that the phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria were predominant. Six strains grew in the presence of chlorpyrifos and iprodione. Biochemical characterization showed that all isolates were positive for esterase, acid phosphatase, among others, and they were identified as Pseudomonas, Rhodococcus and Achromobacter based on molecular and proteomic analysis. Bacterial growth decreased as both pesticide concentrations increased from 10 to 100 mg L-1 in liquid culture. The Achromobacter sp. strain C1 showed the best chlorpyrifos removal rate of 0.072-0.147 d-1 a half-life of 4.7-9.7 d and a maximum metabolite concentration of 2.10 mg L-1 at 120 h. On the other hand, Pseudomonas sp. strain C9 showed the highest iprodione removal rate of 0.100-0.193 d-1 a half-life of 4-7 d and maximum metabolite concentration of 0.95 mg L-1 at 48 h. The Achromobacter and Pseudomonas strains showed a good potential as chlorpyrifos and iprodione-degrading bacteria.

This study provides the basis for implementing a continuous treatment system for wastewater containing a pesticide mixture formed by atrazine, iprodione, and chlorpyrifos. Two fungal strains (Verticilium sp. H5 and Metacordyceps sp. H12) isolated from a biomixture of a biopurification system were able to remove different pesticide concentrations (10 to 50 mg L−1) efficiently from the liquid medium; however, the half-life of the pesticides was reduced and characterized by a T1/2 of 5.4 to 9.2 d for atrazine, 3.7 to 5.8 d for iprodione, and 2.6 to 2.9 d for chlorpyrifos using the fungal consortium. The immobilization of the fungal consortium in alginate bead was effective, with the highest pesticide removal observed using an inoculum concentration of 30% wv−1. The packed-bed reactor with the immobilized fungal consortium, which was operated in the continuous mode at different flow rates (30, 60, and 90 mL h−1), required approximately 10 d to achieve removal efficiency (atrazine: 59%; iprodione: 96%; chlorpyrifos: ~85%). The bioreactor was sensitive to flow rate fluctuations but was able to recover performance quickly. The pesticide metabolites hydroxyatrazine, 3,5-dichloroaniline, and 3,5,6-trichloro-2-pyridinol were produced, and a slight accumulation of 3,5,6-trichloro-2-pyridinol was observed. Nevertheless, reactor removal efficiency was maintained until the study ended (60 d).

Biosurfactants, a wide group of compounds produced by different microorganisms, generally have less toxicity and are more biodegradable than synthetic surfactants. Biosurfactant-producing bacteria can be found in contaminated environments, such as soils receiving pesticide applications constantly, or in pesticides treatment systems where microorganisms are adapted to biodegrading pesticides. Five pesticide-tolerant bacteria previously isolated from a pesticide biopurification system were evaluated as biosurfactant-producers. Pseudomonas rhodesiae C4, Rhodococcus jialingiae C8 and Pseudomonas marginalis C9 strains were positive in qualitative tests. Biosurfactant production by these strains using Bushnell-Haas medium with olive oil at 2% (w/v) was evaluated as emulsification index, oil displacement, droplet collapse test and surface tension. After 144 h, these strains showed a similar emulsification index of >55%. The two Pseudomonas (C4 and C9) strains showed lower superficial tension compared with Rhodococcus strain (C8)—34.47, 37.44 and 47.55 mN/m for strains C4, C9 and C8, respectively. The chemical characterization of the biosurfactants revealed the presence of glycolipids in P. rhodesiae (C4) and glycopeptides in P. marginalis (C9). The degradation of chlorpyrifos increased from 39.2% to 51.6% when biosurfactants produced by P.rhodesiae (C4) were added (10%) with respect to the control. Therefore, biopurification systems are a relevant source of biosurfactant-producing bacteria with environmental biotechnology applications.

The present study aimed to identify novel microbial producers of bioemulsificant compounds from Antarctic soils. Fifty-nine microbial strains were isolated from five different locations at South Shetland Islands, Antarctica, and screened for biosurfactant production by β-hemolytic activity. Strain So 3.2 was determined as bioemulsifier-producer and identified by phenotypic and molecular characterization as Streptomyces luridus. Emulsification activity, oil displacement method and drop-collapsing test were performed to evaluate the biosurfactant activity with different oils and hydrocarbons using two different culture media (Luria Bertani and Bushnell Haas in the presence of different carbon sources: glucose, glycerol, olive oil and n-Hexadecane). Cell free supernatant of Bushnell Haas culture supplemented with n-Hexadecane showed the best results for all tests. Emulsification of hydrocarbons exceeded 60%, reaching up to 90% on oil with high API grade, while displacement tests ranged from 8 cm to 4 cm in diameter according the culture media and tested oils. Our results revealed that Streptomyces luridus So3.2 is able to produce bioemulsifiers capable of emulsifying hydrocarbons and oils, which could be used in different biotechnological applications, particularly for bioremediation of environments contaminated by oil leaks.