Using ultra high-resolution mass spectrometry to characterize the biosorbent Euglena gracilis and its application to dysprosium biosorption

Description

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
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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