Study of nanofibrous membranes for application in post harvest technology

Harmzen, Elrika (2014-04)

Thesis (MSc)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Grapes are lost annually due to spoilage by Botrytis cinerea. Botrytis cinerea is currently controlled using fungicides and SO2 fumigation in storage rooms but with limited success. Although these techniques have been used for decades they have been associated with numerous of disadvantages. Fungicides are restricted from being used during storage due to legislation and toxicity of the fungicides present on the surface of the berries. SO2 fumigation does not kill the dormant infections present inside the grape tissue and if the SO2 concentration is too high the berries are damaged. During this study two different polymer nanofibrous platforms was synthesized in an attempt to prevent the rotting effect of B. cinerea. The first polymer was modified to yield a polymer with a positively charged quaternized nitrogen moiety, which was subsequently reacted with sodium metabisulfite through an ion exchange process. The modified polymer was electrospun into nanofibrous mats for the benefit of the nanofibers’ high available surface area. A further functionalization was done to increase the quantity of sodium metabisulfite on the surface of the polymer nanofibers. Sodium metabisulfite salt released SO2 gas upon reaction with water vapour present in the atmosphere which resulted in the inhibition of conidial germination of B. cinerea. The second polymer was synthesized and then electrospun into polymer nanofibrous mats followed by chemical modification of the electrospun polymer nanofibers. This post-electrospun modification resulted in the covalent attachment of a fungicide-derivative to the surface of the polymer nanofibers. The fungicide-derivative showed excellent inhibition of B. cinerea mycelium growth. Anti-fungal studies were conducted using the two modified polymer nanofibrous mats against B. cinerea to evaluate these nanofibrous surfaces as B. cinerea inhibiting membranes. Results indicated that B. cinerea conidial germination and mycelium growth were successfully inhibited.

AFRIKAANSE OPSOMMING: Druiwe bederf jaarliks weens die verrottende effek van die fungi Botrytis cinerea. Botrytis cinerea word tans beheer deur gebruik te maak van swamdoders en swaweldioksied (SO2) besproeiings in stoorkamers, maar met beperkte sukses. Alhoewel hierdie tegnieke al vir dekades in gebruik is, word dit geassosieer met verskeie probleme. Die gebruik van swamdoders word in stoorkamers verbied, weens die moontlike skadelike inname daarvan deur die mens aangesien die swamdoders op die druiwe se oppervlakte teenwoordig is. SO2-gasbesproeiings maak nie dormante infeksies binne-in die druiwe self dood nie en indien SO2 -konsentrasies te hoog is kan dit die druiwe beskadig. Tydens hierdie studie is twee verskillende polimeer-nanoveselplatforms gesintetiseer met die doel om die verrottende effek van B. cinerea te voorkom. Die eerste polimeer is aangepas met ’n primêre amienverbinding met die doel dat dit deur ‘n opvolgende modifikasiereaksie verander om sodoende ’n polimeer met ‘n kwatenêre ammoniumgroep te verkry. Die doel van die kwatenêre eienskap is dat ioniese uitruiling plaasvind tussen die anioon van die polimeer en die natruimmetabisulfiet-anioon van die sout. Die voorbereide kopolimeer is geëlektrospin in nanoveselmatte deur middel van die enkelnaald-en-enkelbal-elektrospintegniek om SMI-qC12 nanovesels te lewer wat gefunksionaliseer is. Die nanoveselmatte is na die elektrospinproses verder aangepas om die hoeveelheid natruimmetabisulfiet op die oppervlak van die nanovesels te verhoog. Die natruimmetabisulfiet stel SO2-gas vry sodra dit in aanraking kom met waterdamp in die lug wat ’n beperkende effek op spoorontkieming van B. cinerea tot gevolg het. Die tweede polimeer is voor en na die elektrospinproses gefunksionaliseer met gesintetiseerde organiese verbindings (swamdoder). Die aanpassing van die polimeer met die organiese verbindings het plaasgevind op ‘n kovalente wyse om te verhoed dat die organiese verbinding vrygelaat word tydens gebruik. Die organiese verbindings het effektiewe beperking van miselium-groei getoon. Anti-swamstudies is uitgevoer tussen die twee gefunksionaliseerde polimeer platforms en B. cinerea om die oppervlaktes van die gefunksionaliseerde polimeer/nanovesels te evalueer as B. cinerea beperkende platforms. Resultate het aangetoon dat spoorontkieming en miselium groei van B. cinerea suksesvol beperk is.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/86771
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