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Streptomyces has many advantages for exploration in biotechnological applications because of their ability to elaborate a multitude of bioactive molecules and secondary metabolites. Despite the importance of this genus in biotechnology, biofilm formation in Streptomyces is under-investigated. The objective of this research is to adapt two assays for the assessment of biofilm formation in Streptomyces. In the present investigation, we assess and follow biofilm formation in eight Streptomyces strains using quantitative and qualitative methods. The quantitative study based on a staining of the retained biomass in the microtiter plate with crystal violet “5%” and destaining using ethanol/acetone mixture, the concentration of crystal violet in the alcoholic solution reflect the intensity of the attached biofilm. On the other hand, the qualitative one consists of using modified freeman’s method a modified congo red agar method based on the color of colonies. Quantification of biomass by crystal violet staining method confirmed that Streptomyces bellus A43 and Streptomyces bellus A61 are biofilm-forming and this ability increase with the period of incubation. Our results showed that sixStreptomyces strains arenon-slime producing/non-biofilm forming. Two Streptomyces strains are slime producing/biofilm forming; this character vanishes at five days. Further research on genes responsible for biofilm formation in Streptomyces is highly recommended for better understanding of the phenomenon.

The choice of the best support for microbial adhesion can improve the start-up speed and efficiency of dairy wastewater treatment by biofilm bioreactors. In this study, three substrates were tested: PP (polypropylene), PET (Polyethylene terephthalate), and PVC (polyvinyl chloride). By using the contact angle method, the surface physicochemical characteristics of the bacterium, inert substrates, and substrates after dairy wastewater (DWW) conditioning film were measured to understand its impact on adhesion as well as the most suitable material to optimize bacterial adhesion. DWW conditioning film affects the physicochemical characteristics of plastic supports and improves the initial adhesion of bacteria to substrates. Results of initial adhesion tests for untreated and treated supports showed differences in how bacterial cells adhered to substrates. Before treatment, PVC and then PP showed a significant adhesion capacity, double that of PET. After modifying by DWW, initial bacterial adhesion increased by 106 (105 to 1011 CFU/cm2) and PVC demonstrated the highest adhesion capacity, followed by PP and finally PET. Therefore, before the modification of the supports by DWW, PP and PVC are in the same rank for the initial bacterial adhesion and after the modification, PVC seems to be the best for initial bacterial adhesion.