AGROBIOLOGIA
Volume 11, Numéro 2, Pages 2801-2809
2021-12-29

Inventory For Biologically-actives Substances (antimicrobial, Proteolytic, Hemolytic, And Biosurfactants) Of Marine Bacteria Isolated From The Red Algae "asparagopsis Armata"

Authors : Badis Abdelmalek . El Hattab Mohamed .

Abstract

Description of the subject: Screening has always been the essential way to obtain new microorganisms with new molecules. This screening was carried out based on qualitative measurements followed by a quantitative study of all the activities related to industrial and environmental interests, namely, the biosurfactant power (tensioactive character), proteolytic (protease), antimicrobial (antibiotic), and hemolytic activity. Objective: The objective of this work was to isolate, identify and evaluate the biotechnological properties (antimicrobial, proteolytic, hemolytic, and surface activity) of bacterial strains newly isolated from the red alga Asparagopsis armata collected from the Mediterranean coast of Algeria on the East of Tipaza (GPS coordinates: 2°39' 00 '' East, 36°37' 12 '' North). Methods: Twenty-five marine bacteria isolated from the red algae Asparagopsis armata were obtained using a specific medium (Väätänen Nine Salt Solution). The identification of these isolates was based on morphological study (macroscopic and microscopic characteristics) and the different biochemical tests (Catalase, Oxidase, Mannitol-Mobility, and the Respiratory Type). The isolates obtained were screened to produce metabolites with antimicrobial, proteolytic, hemolytic, and surface activities. The study of the antimicrobial activity of the bacterial strains was carried out by the agar- diffusion method, and it was performed against nine bacteria, five Gram-positive and four Gram-negative, two yeasts, and one fungus. Clear inhibition zone formed around plugs were considered indicative of antimicrobial activity. The evaluation of the proteolytic activity in a solid medium of bacterial strains was carried out using a simple and practical method, widely used in screening programs for enzyme-producing microbial strains. It is based on the inoculation of bacterial strains onto skimmed milk agar plates containing casein as a protein substrate. This qualitative test is visualized by the diffusion of secreted proteases into the agar while hydrolyzing the milk caseins, resulting in the appearance of a transparent halo around the colony. The third activity consists of the production of extracellular biosurfactants by the determination of the oil displacement and hemolytic activities. Results: The results obtained allowed us to classify the twenty-five isolates in two different micromorphological genres, 9 strains of the genus Staphylococcus (Gram-positive, Coccis, Immobile bacteria) and 16 strains of the genus Bacillus (Gram-positive bacteria, Bacilli, and Mobile). Regarding the biochemical and metabolic characteristics, all the isolated strains are catalase-positive, 16 strains are oxidase-positive while the other strains are oxidase-negative and all strains are facultative aero-anaerobes. In total, 13 isolates from 25 bacterial strains screened for their potential to produce antimicrobial molecules as following: The most sensible are: Saccharomyces cerevisiae (21mm), Candida albicans (20mm), Listeria monocytogenes (20mm) and Agrobacterium tumefaciens (18mm), with a lesser degree: Bacillus subtilis (15mm), Aspergillus brasiliensis (15mm), Pseudomonas aeroginosa (14 mm) and Escherichia coli (13mm) and with the smallest diameters: Staphylococcus aureus (10mm) and Micrococcus luteus (9mm). Fourteen strains were selected as proteases producers with largest halos (dh/dc ratio varied between 1.02 and 1.59). Seventeen strains have hemolytic-positive activity between them 13 isolates showed a considerable biosurfactant production (6 and 8.5cm of DDP was noticed at 48 to 72h of incubation). Conclusion: These microorganisms can be used as a biotechnological alternative for various environmental and industrial applications. This study will be followed by the selection of the most efficient strains for production studies and optimization of these activities.

Keywords

Marine bacteria ; Asparagopsis armata ; antimicrobial activity ; proteolytic activity ; hemolytic ; biosurfactants