Chlorella vulgaris as soil amendment: influence of encapsulation and enrichment with rhizobacteria

Several trials with five plant growth-promoting rhizobacteria (PGPR) and the chlorophyte Chlorella vulgaris were carried out in order to look for the consortia that could show the best interactions, giving rise to improved growth of mixed cultures. Pseudomonas putida, Serratia proteomaculans and Stenotrophomonas maltophilia were the chosen bacteria for the consortia with Chlorella, while the proportions of microalgae/bacteria tested were 2:1, 3:1 and 3:1, respectively. Three replicates of 20 treatments were performed and studied, after sowing 20 seeds per replicate, for each of the consortia. Plantlets were left to grow for a two-week period. Maltodextrin (MD) and arabic gum (GA) or gelatine (G) were used as coats for the freeze-dried biomass microbeads. Longest roots were obtained with the consortium Chlorella:Serratia but encapsulates of Chlorella:Stenotrophomonas gave rise to meadow clover plantlets with the highest root and shoot system dried biomass, especially with coating proportions of 1:1 MD:G and MD:GA. Results obtained with this last consortium suggested some interactions with the plant metabolism, as well as some synergistic effects between Chlorella and bacteria.