Enhancing Algal Biomass and Lipid Production through Bacterial and Fungal Co-Culture

This thesis investigates the effects of co-culturing microorganisms including 37 yeast, 38 bacteria, nine diazotrophic cyanobacteria, and three fungi on biomass and lipid production in fresh- and saltwater algae. Algal lipid content was measured using Nile Red method and gravimetric techniques. Among the algal strains tested, freshwater Coelastrum sp. 46-4, and saltwater Cricosphaera sp. 146-2-9, showed enhanced biomass yield and lipid content in response to co-culture with bacteria, cyanobacteria, and fungi. While co-culture with yeast caused inhibition of algal productivity, no difference in algal productivity was observed between nitrogen-free diazotrophic cyanobacterial co-culture and nitrogen-replete monoalgal culture. Results indicated that extracellular compounds from the freshwater bacteria Pseudomonas stutzeri and marine fungus Fusarium sp. significantly account for stimulation of lipid accumulation within algal cells, while co-cultivation with live microorganism cells stimulated biomass production in algae

Control of algal growth on greenhouse surfaces using commercial algaecides

Greenhouses and nurseries provide ideal environments for facilitating the formation of nuisance algal mats. Algal growth poses safety concerns to horticulturists and stimulates the propagation of unwanted plant pests and pathogens. To date, few strategies and data are available to effectively manage algal problems. The effectiveness of five algaecides was tested on two varying surfaces of greenhouses in situ to elucidate the efficacy of chemical methods of removing algae. Moreover, Nostoc commune (Vaucher ex Bornet & Flahault) was treated on ceramic tiles in vitro, as it is a common alga in greenhouses and nurseries. We found that each algaecide had different effects, depending on the chemical applied, the surface to which the chemical was applied, and finally the types of algae that were targeted. Algaecides across the surfaces tested demonstrated that algal cell characteristics and communal makeup played an important role in algaecide efficacy, where mucilaginous algae were replaced by sheath-forming filamentous cyanobacteria. We found sodium carbonate peroxyhydrate to be the most effective chemical in terms of controlling Nostoc on tarp, gravel, and ceramic surfaces

Growth of Diatom Fistulifera Alcalina in Bacterial Co-culture and Comparative Mitogenomics of Fistulifera Species

Diatoms are excellent biological models of growth and intracellular oil generation. The productivity and compounds of diatoms, especially oils, support aquatic food chains and human medical and industrial needs. The qualities that made diatoms prolific producers, specifically diatom physiological features such as growth rates with intracellular lipid storage in alkaline environments, are however poorly understood. Another physiological aspect that remains unexplored is the effects of bacteria on the growth and lipid production of alkaliphilic diatoms. More studies, especially co-cultures, are needed for advances in diatom biology and strain performance for the algal biotechnological field. Besides physiology, diatom genetics using next-generation methods are used to reveal the basis for diatom success in growth and productivity, though more genomic data and comparative studies are needed to fully uncover these mechanisms in diatoms. To improve our understanding of alkaliphilic diatom physiology and genetics, specifically we need to understand 1) what stimulates diatom successful growth in alkaline environments and in culture, 2) diatom biodiversity especially at the species level, 3) algal physiology in the context of how diatom productivity may be enhanced by bacteria, and 4) the biological basis for the extraordinary growth rates of diatoms and their success in alkaline environments. To explore ways in which we can improve our understanding of alkaliphilic diatom physiology and genetics this dissertation aimed to first isolate alkaliphilic algae and explore their alkalinity optimums along with their growth rates and lipid production. A high lipid producing diatom Fistulifera alcalina was isolated and characterized using 18S rRNA and rbcL molecular phylogeny. To further explore the diversity within Fistulifera and simultaneously exploit diatom microbiomes, Lake Okeechobee was sourced for alkali-tolerant to alkaliphilic bacteria associated with diatoms to co-culture with F. alcalina. Results indicated that alkaliphilic bacteria like Bacillus horikosshi were effective in modulating growth and lipid content of F. alcalina. To explore the basis for the extraordinary growth rates in F. alcalina and its’ success in alkaline environments, the mitochondrial genome was sequenced and compared to F. solaris. Results indicate that alkaliphilic diatoms may have streamlined genomes and are impetus for further genome sequencing and physiological studies