Abstract

Background: A small subset of the vast diversity of microalgae present in the Hawaiian Islands was isolated, cultured, and investigated for potential industrial applications. This subset was composed of either newly reported isolates of Chlorophytes and Bacillariophytes or several species already well established in local aquaculture.

Methods: Isolates were identified based on 18S rRNA sequence or morphology where applicable. Isolates were profiled for constitutive biochemical composition using biomass harvested in late log phase under nutrient replete conditions.

Results: New isolates examined included Acrochaete, Asterarcys, Chlamydomonas, Chlorella, Desmodesmus, Marinichlorella, Micractinium, Monoraphidium, Nannochlorum, Parachlorella, Picochlorum, Podohedriella, Mychonastes, Scenedesmus, Tetraselmis and some diatoms. Several had favorable profiles for potential use in a fuel and feed biorefinery, for wastewater treatment with CO2 capture, or for more specialized products with options for cultivation as phototrophs or facultative heterotrophs in freshwater or saltwater. Whole biomass showed a useful combination of protein and lipids, good in vitro digestibility, and presence of key essential amino acids lysine, methionine, and cysteine. Many isolates had predominantly C16 to C18 fatty acids while a few had polyunsaturated fatty acids with options for ω-3, ω-6 and ω-9 combinations. Marinichlorella kaistiae, a new species for Hawai'i, proved suitable for very large-scale cultivation and conversion into biofuel, and its fatty acid profile varied with cultivation in freshwater or salt water. Several freshwater diatoms, all of which proved scalable including in saline conditions, may be new representatives of Humidophila, Sellaphora and Nitzschia. The composition of an exudate produced by Mayamaea, a taxon previously isolated in Hawai'i in lava tubes, was determined to be a unique mannose-rich exopolysaccharide.

Conclusion: Several Hawai'i-sourced strains described here are already of benefit in biofuels and treatment of effluents including CO2, and are anticipated to have value in next generation cosmetics and ‘cosmeceuticals’ to impact skin appearance, health and disease applications. Moreover, with protein having higher intrinsic value than biofuels, it is informative to characterize algal strains at a stage in biomass production that reflects high protein with constitutive lipid content.

Keywords: Microalgae, 18S rRNA sequence, bioproducts, bioenergy, biorefinery, feed, food, cosmetics, wastewater, remediation.

Graphical Abstract