Plants are potential sources of valuable recombinant and native proteins that can
be purified for pharmaceutical, nutraceutical, and food applications. Transgenic rice and
corn germ were evaluated for the production of novel protein products. This dissertation
addresses: 1) the extraction and purification of the recombinant protein, human
lysozyme (HuLZ), from transgenic rice and 2) the processing of dry-milled corn germ
for the production of high protein germ and corn protein concentrate (CPC).
The factors affecting the extraction and purification of HuLZ from rice were
evaluated. Ionic strength and pH was used to optimize HuLZ extraction and cation
exchange purification. The selected conditions, pH 4.5 with 50 mM NaCl, were a
compromise between HuLZ extractability and binding capacity, resulting in 90% purity.
Process simulation was used to assess the HuLZ purification efficiency and showed that
the processing costs were comparable to native lysozyme purification from egg-white,
the current predominant lysozyme source.
Higher purity HuLZ (95%) could be achieved using pH 4.5 extraction followed
by pH 6 adsorption, but the binding capacity was unexpectedly reduced by 80%. The
rice impurity, phytic acid, was identified as the potential cause of the unacceptably low capacity. Enzymatic (phytase) treatment prior to adsorption improved purification,
implicating phytic acid as the primary culprit. Two processing methods were proposed
to reduce this interference: 1) pH 10 extraction followed by pH 4.5 precipitation and pH
6 adsorption and 2) pH 4.5 extraction and pH 6 adsorption in the presence of TRIS
counter-ions. Both methods improved the binding capacity from 8.6 mg/mL to >25
mg/mL and maintained HuLZ purity.
Processing of dry-milled corn germ to increase protein and oil content was
evaluated using germ wet milling. In this novel method, dry-milled germ is soaked and
wet processed to produce higher value protein products. Lab-scale and pilot-scale
experiments identified soaking conditions that reduced germ starch content, enhanced
protein and oil content, and maintained germ PDI (protein dispersibility index). Soaking
at neutral pH and 25 degrees C maintained germ PDI and improved CPC yield from defatted
germ flour. CPC with greater than 75% protein purity was produced using protein precipitation or
membrane filtration.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-08-7116 |
| Date | 2009 August 1900 |
| Creators | Wilken, Lisa Rachelle |
| Contributors | Nikolov, Zivko L. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | application/pdf |
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