General awareness exists regarding the detrimental effects of pesticides use and management on the environment; therefore, their removal from contaminated matrices has become a major concern in the field of environmental engineering and science. Nowadays, biological methods have attracted considerable attention and many microorganisms have been isolated, characterized and recognized as responsible for pesticide degradation. This review shows the current evidence and results obtained in the last decades that support the use of microorganisms belonging to the Streptomyces genus as a promising biotechnological tool for bioremediation of pesticides contaminated matrices. This review covers the degradation of pesticides in both liquid and soil systems, soil slurries and biobed biomixtures, by single, consortia, free and/or immobilized Streptomyces strains.

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.

Potato waste was processed and used as a sole substrate for simultaneously producing antifungals and biopigments usingStreptomycesspp. Out of three differentStreptomycesisolates, strain SO6 stood out due to its ability to produce antifungals against economically important fungal phytopathogens and intracellular biopigments using potato waste powders without additional nutrients. This strain also showed the potential to secrete a broad range of enzymes for fermentation of eight sugars that could be involved in potato waste bioconversion. The results of the fermentation assay indicated thatStreptomycessp. strain SO6 degrades potato wastes during submerged fermentation, diminishing total dry weight and increasing reducing sugars from 0.3 to 3.6 mg·mL⁻¹and total proteins from 70.6 to 187.7 μg·mL⁻¹. The results showed thatStreptomycesstrain SO6 was able to convert the potato waste into 0.96 mg·g⁻¹of diffusible antifungals and 1.75 mg·g⁻¹of reddish-purple biopigments. On the contrary, an absence of pigment production was observed during the fermentation of the commercial medium used as reference. According to our results, replacement of commercial culture media with available low-cost agroindustrial wastes for producing bioactive chemicals is a real opportunity to enhance theStreptomycespigment production and antibiotic sustainability with cost-competitiveness. To our knowledge, this is the first report on the simultaneous production of biopigments and diffusible antifungal antibiotics produced byStreptomycesspp. using potato solid waste as the sole nutrient source.