Evaluation of the microbial risks associated with duckweed cultivation on agro-industrial wastewaters

In Europe, the livestock sector is one of the biggest consumers of plant protein, with 70% being directed to pig and poultry feed alone. It is a challenge for the sector to meet this demand, resulting in a reliance on imported soy protein in several countries. Duckweed species are free floating freshwater plants belonging to the family Lemnaceae. These plants can be found worldwide and are characterized by high growth rates and high protein content (up to 35% per unit dry weight). In addition, these plants have been shown to grow on a range of high nutrient load, agricultural and municipal waste streams. Duckweed species therefore offer sustainable, circular economy opportunities to couple wastewater valorisation with high protein content plant growth for potential animal feed applications. However, a critical aspect of any such process would be to evaluate the potential microbiological risk of pathogenic bacterial associations with wastewater grown Duckweed. In this study, duckweed was cultivated on farmyard wastewater (dairy milking parlour and yard waste) and meat processing wastewater which underwent pre-treatment prior to duckweed growth. Duckweed was cultivated over a 28-day period, after which wastewater and frond associated bacteria were isolated via culture-based methods, and additional cultivation was conducted to allow for metagenomic sequencing of wastewater and duckweed associated communities. The dominant genera recovered from Duckweed contained several plant associated bacteria, including Pseudomonas, Comamonas, and Stenotrophomonas. These genera have previously been identified as common community members of duckweed associated microbiomes. While some pathogenic associations were observed within wastewater samples, a decrease was seen over time. Valuable fractions (protein and carbohydrate) were also extracted from duckweed following wastewater cultivation, and assessment of the microbiological safety was conducted. Significance of the findings are discussed within this thesis.

Grantor dc:publisher

University College Cork

Year dc:date.issued

2025

Author dc:creator

• Bannon, Leah Bridgit

Advisor dc:contributor.advisor

• O'Leary, Niall

• Wastewater
• Duckweed
• Microbiome
• Plant growth promoting bacteria
• Metagenomic
• Feed Safety
• Wastewater valorisation

Statement dc:rights

• © 2025, Leah Bannon.

Licence dc:rights.uri

• https://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10468/18927

OAI identifier oai:identifier

oai:cora.ucc.ie:10468/18927