Balch , Gordon

Euglena gracilis is an enigmatic and adaptable organism that has great bioremediationpotential and is best known for its metabolic flexibility. The research done in this dissertation addresses (1) how growth conditions impact cellular composition, and (2) how chemometric approaches (such as statistical design of experiments and artificial neural networks) are viable alternatives to the conventional biosorption models for process optimization. Using high-resolution mass spectrometry for biosorbent characterization is a powerful way to assess the chemical characteristics of lyophilized and fractionated cells with high precision, especially to screen for compound classes that may have potentiality for rare earth element removal. Growth conditions impacted cellular composition and separated size fractions of cells yielded different molecular/chemical properties as described by compositional abundances, thus different biosorptive potential. Untargeted analysis demonstrated that exponential dark-grown cells with glucose supplementation were abundant in polyphenolic- and carbohydrate-like compounds, molecular species highly involved in rare earth element binding. Light grown cells had more heterogeneity and the highest molecular weighted fractions from light grown cells (fraction D) had the most abundances of polyphenolic- and protein-like structures. Chemometric modeling used identified the best and worst conditions for iii dysprosium sorption and showed that pH had the most significant influence on bioremoval. Bioremoval ranged from 37% at pH 8 to 91% at pH 3 at Dy concentration ranging from 1 to 100 μg L-1. The work presented in the PhD dissertation will aid in understanding the chemical characteristics of biosorbents by using a Van krevelen analysis of elemental ratios whether algal cells are grown in different environmental growth conditions, or when algal cell are size fractionated. This is especially applied for the screening for metal binding potentiality to Dysprosium. Chemometric methods provide an alternative method for the investigating factors for bioremoval, and applications for process optimization and for real-world applications. This dissertation will aid in understanding chemical characteristics when a biosorbent is grown in a given condition and which factors are important for rare earth element (REE) bioremoval. The significance of this work aims to look for alternate ways to screen biosorbents and using a more efficient experimental design for REE bioremoval.

Author Keywords: bioremoval, biosorption, chemometrics, dysprosium, euglena, mass spectrometry