Halpin, Grace (2019) Lactose and Lactic acid Biosensor Development for Dairy Sample Analysis. Masters thesis, National University of Ireland Maynooth.

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Abstract

Rapid and selective monitoring of small molecules is important in relation to fermentation process control where optimisation and scale up relies on accurate measurement of species such as lactose and lactic acid. Currently, chromatographic approaches such as HPLC are the most commonly used methods for such analysis but can be both costly and time consuming. Here, development of an enzymatic biosensor for rapid quantitation of key analytes in dairy samples (whey permeate, milk protein concentrates and fermentation samples) is presented. This involved 1st and 2nd generation biosensor fabrication using Chitosan/Enzyme(s)/Chitosan/GA or PEGDE configuration utilising the enzymes GOx, β-gal and LOx. Due to the complex matrix of dairy samples, solution phase mediation at carbon transducers was used to lower the operating potential (Eapp = 0.3 V vs. Ag/AgCl), improving sensitivity and eliminating any contribution from endogenous background electroactive species. Following sensor design and development, CV and CC realised analytical data for the lactose sensor with linear range 5.83 x 10-3 to 1.65 x 10-2 M, sensitivity 9.41 x10-4 C cm-2 mM-1 and LOD of 1.38 mM. In the case of the lactate biosensor, a linear range 9.9 x 10-4 to 5.66 x 10-3 M, sensitivity 1.44 x 10-3 C cm-2 mM-1 and LOD of 0.54 mM was realised. Further investigation into lactate sensing involved use of the heterocyclic quinoid species 1,10-phenanthroline-5,6-dione which acted as a proton and electron acceptor in relation to FADH2 cofactor regeneration. Graphite ink was formulated and utilised as an underlying conductive layer for LOx enzyme immobilisation and enzymatic polymerisation of 1,10-phenanthroline-5,6-dione at a GC electrode, resulting in a linear range of 0.74 – 2.44 x 10-3 M, sensitivity of 4.11 x 10-4 C cm-2 mM-1 and LOD of 0.06 mM. On-site analytical performance was examined in diluted fermentation media, comparing well to the established HPLC-RI separation approach, with 93 -100 % correlation for lactose analysis and 72 – 96 % correlation for lactate analysis over the range of sampling time points investigated (lactose levels ranged 4 – 306 mM and lactate levels 69 – 805 mM). Data generated in this thesis provides evidence that the developed biosensors have enormous potential for on-site industry deployment with proven capability for accurate, reliable measurement of lactose and lactic acid levels in a range of dairy samples.

Item Type:	Thesis (Masters)
Keywords:	Lactose; Lactic acid; Biosensor Development; Dairy Sample Analysis;
Academic Unit:	Faculty of Science and Engineering > Chemistry
Item ID:	16849
Depositing User:	IR eTheses
Date Deposited:	12 Jan 2023 12:06
URI:
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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