Date of Award

5-2011

Document Type

Doctoral Thesis

Degree Name

Doctor of Philosophy

Department

Biological & Pharmaceutical Sciences

First Advisor

Dr Michael Hall

Second Advisor

Dr Mary Concannon

Abstract

Commercial preparation of seaweed extract from Ascophyllum nodosum, for use as fertilizer and soil improver, produces a residue which requires remediation. This residue is rich in nutrients and offers potential for other added-value products. The residue’s composition and microbial flora were studied, a microbial digestion system was developed, and extracts were screened for anti-hyaluronidase and anti-elastase activities.

The residue had a pH of 8.61±0.39, 16% (w/w) TS which comprised 40.6% minerals, 29.5% fibre, 20.9% lipid, 4.9% protein and 0.48% polyphenols. The microbial digestion included an initial 3-day anaerobic phase during which pH decreased from 9.12 to 7.89. At day 3, solubilized material was decanted to delay metabolite inhibition, an inoculum was added, followed by a 10-day aerobic digestion. The rate of digestion (decrease in insoluble material of 28.6±14.2% over 13 days) was influenced by the initial insoluble (R2=0.773) and soluble (R2=0.672) matter, the pH at the beginning of the aerobic phase (R2=0.528) and by accumulation of solubilized digestive products. A compositional analysis of the insoluble material after digestion showed the lipid content of the residue was 96% digested, and protein content increased by 82.4%. Organic acid analysis (HPLC) revealed the presence and consumption of oxalic, formic, lactic and acetic acids during the anaerobic and/or aerobic phases. Microorganisms of A. nodosum residue (Brochothrix thermosphacta, Bradyrhizobium japonicum, Pseudomonas sps. and Enterobacter amnigenus) and the inocula employed (Leclercia adecarboxylata, Serratia sp., Klebsiella pneumoniae, E. coli and Aspergillus versicolor) were identified and characterised.

Soluble material collected from the digestion exhibited stronger anti-hyaluronidase activity than A. nodosum plant (IC50 values of 0.25 mg/mL and 0.70 mg/ml, respectively). A. nodosum and L. hyperborea seaweeds were treated and screened for hyaluronidase and elastase inhibitors. A. nodosum treated with bromelain showed potential for anti-elastase activity. The data shows that seaweed residue has further potential for commercial exploitation.

Access Level

info:eu-repo/semantics/openAccess

Project Identifier

info:eu-repo/grantAgreement/HEA/TSR Strand 1//IE//

Coverage

July 2024

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