Investigating Culture and Products of Sea Vegetables
Project Description
The objective of this project is to investigate the chemical composition of macroalgae for safe food production and to identify and optimize production of antimicrobial compounds present in local macroalgae.
Aquaculture of macroalgae on the coast of Maine produces 33,000 pounds of biomass per acre and consumes excess nutrients and CO2 from seawater in the process. Nutrient runoff from agricultural areas, lawn fertilizers, and waste water, lead to harmful algal blooms, which reduce water oxygen concentration and negatively impact marine life. The ecological and economic consequences culminate in beach closure. Macroalgae mariculture during winter months removes excess nitrogen from aquatic ecosystems, improving ecosystem health while producing algal biomass of commercial use for food, cosmetics, fertilizer, and health supplements.
Results of this project will expand the use of economically important algae to profitable medical applications focused on inhibiting drug-resistant human pathogens, such as methicillin-resistant Staphylococcus aureus (MRSA). MRSA is responsible for over 18,000 deaths per year in the U.S. and is a major cause of hospital- and community-acquired infections in Maine. Because MRSA strains are antibiotic resistant, there is critical need for novel therapeutics. Natural products from macroalgae are promising sources of anti-infectives and may be useful against Staphylococcus infections.
Results and Accomplishments
The brown and red macroalga are abundant in the intertidal zones of the Gulf of Maine despite considerable wave action and herbivore pressure. This implies that algae may contain defense mechanisms that protect them against herbivore and microbial attack. The current project investigates the antimicrobial properties of algal secondary metabolites against human pathogens. Previous results showed that algae extracts were mostly effective against gram positive pathogens. Project personnel focused on the gram-positive methicillin-resistant Staphylococcus aureus, the community-associated MRSA strain USA300 that has become a common cause of infections in health care environments, and Staphylococcus aureus Newman that has been intensively used in animal studies of staphylococcal infections. However, after modifying the extraction technique, the team also found activity against gram negative human pathogens.
To determine the antimicrobial properties of algae extracts, solvent extracts were prepared from ground algae tissue. Previous results showed the polar solvent methanol was more effective in extracting antimicrobial compounds compared to the non-polar solvent pentane. Therefore, project personnel compared methanol extracts to extractions with dichloromethane, a solvent of intermediate polarity as well as to extractions with water to evaluate the potential of a polar non-toxic solvent. Extracts were pipetted onto sterile disks and added to bacterial strains grown on agar plates. Plates were incubated overnight and the zone of inhibition was measured. Project personnel found water extracts of algae had a greater effect on the inhibition of both bacterial strains than methanol extracts. Extractions with Dichloromethane showed no to very limited antimicrobial activity on all nine bacterial tested strains.
Summary of Data Being Collected
| Data | Type | Quantity | Location |
| Chemical extraction of algae | Algae collected in field | 60 | Biddeford Pool |
| Antimicrobial assays | Laboratory experiments with field collected algae | 60 | Biddeford Pool |
| Microscopic observation | Laboratory experiments with field collected algae | 20 | Saco River |