Immobilization of lactase to Perloza cellulose resins : a thesis was presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University

A bead cellulose matrix, Perloza, was chemically modified by two attachment chemistries to prepare inexpensive resins for immobilization of lactase. A commercial product, the base-activated matrix Eupergit C was studied for comparison. Three types of Perloza (Perloza 100 MT, Perloza 200 MT, Perloza 500 TM) were activated by epichlorohydrin (ECH) to achieve different activation levels. The best result for lactase immobilization was gained at low activation level (activated at 2% NaOH) for two attachment chemistries. The first attachment chemistry studied was that lactase immobilized directly to ECH activated Perloza. The second chemistry again used ECH activation and followed by attachment of the 6-amino caproic acid (ACA) spacer arm and then the lactase. In the first chemistry, Perloza 100-ECH-Lactase obtained the highest activity 11.4 NLU/g (wet resin) over Perloza 200-ECH-Lactase and Perloza 500-ECH-Lactase (40 hours immobilization). In the second chemistry, Perloza 200-ECH-ACA-Lactase retained the highest activity 30.9 NLU/L (wet resin) over Perloza 100-ECH-ACA-Lactase and Perloza 500-ECH-ACA-Lactase. Overall the best results were obtained for the ECH-ACA resins. This best of these results showed about 3 times better immobilization than without ACA spacer arm. The activity of immobilized lactase on Eupergit C obtained was 124~131.3 NLU/g (wet resin) for 24 hours immobilization. Although this result is about four times greater than Perloza, Perloza is a much cheaper matrix. In the storage stability studies, both Perloza and Eupergit C immobilized lactase showed a sharp drop in activity initially within 1 day, then activity loss leveled out. Perloza 200-ECH-ACA-Lactase retained 82% of its original activity after 9 days storage. However, Eupergit-Lactase only retained 39% of its original activity after the same storage period. This result indicated that Perloza 200-ECH-ACA-Lactase may possess much better storage stability than that of Eupergit-Lactase. Studies on the inter-relationships between pH. temperature and Perloza immobilized lactase using the substrate (ONPG) indicated that maximum hydrolysis was attained at pH 6.5-7.2 and over a temperature range of 30-42°C. No shift in the pH and temperature optima in comparison to free enzyme was observed as a result of the process of immobilization of lactase on Perloza for both attachment chemistries. The pH-activity curve of Eupergit-Lactase shifted towards more acidic pH values in the pH optimum in comparison to free lactase. The temperature optimum of Eupergit-Lactase shifted towards higher temperature compared to free lactase. This study showed that Perloza has potential for the large scale use as a matrix of lactase immobilization

Full linear perturbations and localization of gravity on f(R,T)f(R,T) brane

We study the thick brane world system constructed in the recently proposed $f(R,T)$ theories of gravity, with $R$ the Ricci scalar and $T$ the trace of the energy-momentum tensor. We try to get the analytic background solutions and discuss the full linear perturbations, especially the scalar perturbations. We compare how the brane world model is modified with that of general relativity coupled to a canonical scalar field. It is found that some more interesting background solutions are allowed, and only the scalar perturbation mode is modified. There is no tachyon state exists in this model and only the massless tensor mode can be localized on the brane, which recovers the effective four-dimensional gravity. These conclusions hold provided that two constraints on the original formalism of the action are satisfied.Comment: v3: 8 pages, 2 figures, improved version with minor corrections, accepted by EPJ

Gravitational resonances on f(R)f(R)-brane

In this paper, we investigate various $f(R)$-brane models and compare their gravitational resonance structures with the corresponding general relativity (GR)-branes. {Starting from some known GR-brane solutions}, we derive thick $f(R)$-brane solutions such that the metric, scalar field, and scalar potential coincide with those of the corresponding GR-branes. {We find that for branes generated by a single or several canonical scalar fields, there is no obvious distinction between the GR-branes and corresponding $f(R)$-branes in terms of gravitational resonance structure.} Then we discuss the branes generated by K-fields. In this case, there could exist huge differences between GR-branes and $f(R)$-branes.Comment: 17 pages, 14 figures, published versio