Physiological and biotechnological studies on the microalga Dunaliella, the bacterium Halomonas, and the cyanobacteria Arthrospira and Spirulina.

摘要

A bacterial isolate and a microalga were identified to the genus leveludusing 16S and 18S rRNA gene sequences respectively and· phylogenetic treesudwere constructed. The bacterial isolate belonged to the genus Halomonas andudit was called Halomonas sp. NAH1, whereas the microalga was confirmed asudbelonging to the species Dunalie/la salina GGAP 19/30 which was the source ofud18S rRNA gene. Glycerol production by three strains of the unicellularudmicroalga Dunalie/la (D. parva 19/9, D. parva 19/10, and D. salina 19/30) wasudexplored. The strains were grown in batch cultures in a range of salinities (0.1 4.0udM NaCI). Both intracellular and extracellular glycerol concentrations wereudmeasured. All three strains grew well over the range of salinities with optimumudgrowth for all strains at 0.1 to 0.4 M NaC1. All strains leak significant amounts ofudglycerol in batch cultures. Significant leakage of glycerol into the growthudmedium was found to be an intrinsic property of the three strains tested. Twoudstrains of Dunalie/la salina (GGAP 19/18 and 19/30) were grown in batchudcultures and aerated with different concentrations of G02. Strain 19/18udaccumulated large amounts of ~-carotene under nitrogen limitation whereas theudstrain 19/30 did not. Halomonas sp. NAH1 grew optimally at 1.0 M NaCI andudutilised glucose, glycerol or betaine as the sole source of carbon. Glucoseudsupported the most rapid growth rate. Sensitivity of NAH1 to antibiotics wasuddetermined and tetracycline had the most inhibitory effect on growth. Theudcyanobacteria Arthrospira fusiformis GGAP 1475/8 and Spirulina platensisudUTEX LB 2340 were shown to be only slightly halotolerant with optimum growthudfor S. platensis at 0.1 M NaC1 and for A. fusiformis at 0.5 M NaC1.udPhycobiliprotein content was very low in both strains, but very high proteinudcontent (92.9% of the dry weight biomass) was obtained for S. platensis. Thisudstrain looks very promising for mass cultivation for food and/or feed purposes.udGlucosyl-glycerol was found to be the compatible solute in both A. fusiformisudand S. platensis.