unicellular green algae chlorella spirulina with large cells single-cells with lipid droplets. watercolor seamless

algae algal ameoba bacteria bacterium biodiesel biofuel biology biosynthesis biotech biotechnology border chlorella design diet droplets element energy environment environmental food fuel green horizontal illustration lipid macro medical membrane microalgae microscope molecule natural nature oil organism production pure research science scientific singlecell source spirulina sustainable vegetarian watercolor