2023-24 AEESP Distinguished Lecturer

Professor Edwards will present two lectures in the 2023-2024 Tour:

Lecture 1: "Adventures in anaerobic bioremediation"

Groundwater contamination is a serious threat to global health and prosperity.  Petroleum hydrocarbons, industrial solvents, pesticides, herbicides, and metals are some of the most frequent culprits.  Some microbes have evolved and adapted to transform or detoxify contaminants.  Certain species, such as Dehalococcoides, can dechlorinate the major dry-cleaning solvent tetrachloroethene and the common industrial solvent trichloroethene to the benign product ethene.  Remarkably, these organisms obtain energy for growth from dechlorination, and several successful demonstrations of bioaugmentation, where an aquifer is inoculated with a mixed microbial culture, have led to the development of a viable commercial market for such dechlorinating cultures.  By studying enrichment cultures and their megagenomes, we are learning more about novel interspecies interactions in these remarkable, ubiquitous, anaerobic microbial communities, and their specialized enzymes that catalyze reductive dehalogenation reactions.  Benzene is another problematic contaminant, readily degraded under oxic conditions, but highly persistent in anaerobic environments.  The anaerobic metabolism of benzene is complex and still largely unknown, yet clues are emerging that reveal novel microbes, pathways and enzymes that could be harnessed for cleanup.  Prospects for biodegradation of other contaminants, including the pesticide chlordecone and perfluorinated substances will be discussed.

[Note that the lecture can be tailored to emphasize contaminants of interest.]

Lecture 2: "The complex microbiology of pilot and full-scale anaerobic digestion systems"

Anaerobic digestion (AD) is an effective process for converting organic material into methane and carbon dioxide.  AD is the result of a beautifically intricate and complex interactive microbial ecosystem.  Inexpensive sequencing technology has enabled unprecedented exploration of these ecosystems uncovering thousands of new microbes and putative genes.  Yet how can we extract meaningful and actionable data from these microbiological data?  We have investigated solid-state anaerobic digestion (SS-AD) as a viable alternative for organic waste disposal, particularly in North America where tipping fees are low, because it minimizes the costs of waste pretreatment, mixing, and subsequent wastewater treatment.  We have operated a laboratory SS-AD digester affectionately called "Daisy" for several years.  Daisy comprises six 10L leach beds and is fed a mixture of cardboard, boxboard, newsprint, and fine paper, and varying amounts of food waste.  The addition of food waste results in enhanced fiber conversion, but is this enhanced conversion explained by microbial community composition?  We have also investigated full scale AD systems treating pulp and paper mill waste streams and tracked the associated microbial communities.  These data reveal the importance of time with respect to adaptation of the microbial community and response to perturbations.  Appreciating microbial community dynamics, and in particular different process and metabolic time constants will contribute to improved AD operation.