Date of Publication

11-28-2025

Document Type

Master's Thesis

Degree Name

Master of Science in Chemistry

Subject Categories

Chemistry

College

College of Science

Department/Unit

Chemistry

Thesis Advisor

Rafael A. Espiritu
Rhowell N. Tiozon, Jr., co-adviser

Defense Panel Chair

Emmanuel V. Garcia

Defense Panel Member

Mariafe N. Calingacion
Henry M. Corpuz

Abstract (English)

Rice is a vital staple that sustains more than half of the world's population. However, one of the persistent challenges is in its short shelf life brought about by rancidity. In particular, oxidative rancidity, characterized by the peroxidation of polyunsaturated fatty acids to unstable lipid hydroperoxides, leads to the formation of aldehydes, ketones, and alcohol products that contribute to the characteristic stale, off-flavor, and smell of rancid rice. Lipoxygenase 3 (LOX3) is one of the genes that contribute highly to lipid oxidation; thus, a possible solution to rancidity is its removal or knock-out using gene editing technology. Despite various reports showing the effects of LOX3 knockout, no studies have comprehensively characterized the physicochemical properties of lox3 mutants. Hence, this study analyzed and assessed the physicochemical properties of a CRISPR/Cas9 gene knockout rice sample, focusing on its thermal properties and compositional characteristics. For thermal properties, Differential Scanning Calorimetry (DSC) was used to analyze the enthalpies (gelatinization and amylose-lipid complex) of rice, and thermal gravimetric analysis (TGA) was used to assess the thermal stability and decomposition of the rice. Meanwhile, for compositional analysis, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and liquid chromatography-mass spectrometry (LC- MS) were employed. DSC showed that OsLOX3 knockout lines exhibited higher gelatinization enthalpy than controls, with the difference significant in IRRI154 but not in Samba Mahsuri. In contrast, the amylose-lipid complex enthalpies were lower in both lines, but the differences were not significant. TGA thermograms showed almost identical results between the control and OsLOX3 knockout lines, as did FTIR, which revealed spectra nearly identical to those of the control, suggesting no major changes in overall thermal stability or bulk functional group composition. However, second-derivative spectra in principal component analysis (PCA) showed clustering in IRRI154 between the control and knockout lines, while lacking separation in Samba Mahsuri. By contrast, LC-MS revealed substantial differences in levels of key metabolites associated with oxylipin and other metabolic pathways, as well as higher levels of fatty acids, including oleic acid (18:1). The overall results provide insight into how the absence of OsLOX3 contributes to the reduction in rancidity and may potentially improve the shelf life of rice.

Abstract Format

html

Abstract (Filipino)

Ang bigas ay isang pangunahing pagkain ng mahigit kalahati ng populasyon ng mundo. Subalit, isa sa mga kinakaharap nitong suliranin ay ang maikling panahon na maaring maimbak dahil sa rancidity. Partikular ay ang oxidative rancidity, na kung saan nagsisimula ito sa peroxidation ng polyunsaturated fatty acids na nagbubunga ng unstable lipid hydroperxides na kalaunan ay nagdedegrade at nagiging aldehydes, ketones, at alcohol, mga produkto na nagdudulot ng hindi kanais-nais na amoy at lasa. Ang lipoxygenase 3 (LOX3) ay isa sa mga pangunahing genes na malaki ang kontribusyon sa lipid oxidation. Isang posibleng solusyon sa pagbawas ng rancidity ay ang pag knockout ng OsLOX3 gene gamit ang teknolohiya ng gene editing. Bagama’t mayroon ng pagaaral ukol sa epekto ng pag knockout nito, nananatiling limitado ang komprehensibong pagaaral sa mga pisikokemikal na katangian ng mga lox3 mutants. Kaya ang pagaaral na ito ay sinuri ang iba’t ibang pisikokemikal na katangian ng mga CRISPR/Cas9 gene knockout sampol, na nakatuon sa thermal at compositional properties. Para sa thermal properties, ginamit ang differential scanning calorimetry (DSC) upang analisahin ang enthalpy (gelatinization at amylose-lipid complex) at thermal gravimetric analysis (TGA) sa paganalisa ng thermal stability at profile ng thermal dekumposisyon ng bigas. Samantalang ginamit ang attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy at liquid chromatography-mass spectrometry (LC-MS) upang suriin ang komposisyon nito. Ang DSC ay nagpakita ng mas mataas na gelatinization enthalpy sa OSLOX3 knockout lines kumpara sa kanilang mga kontrol. Ang resulta ay may makabuluhang pagkaikaiba sa IRRI154 ngunit wala sa Samba Mahsuri. Samantala, ang amylose-lipid complex enthalpies ng OsLOX3 knockout lines sa dalawang kultibar ay mas mababa ngunit ang pagbabago ay hindi makabuluhan. Ang mga TGA thermograms ay nagpakita ng halos parehas na resulta sa pagitan ng control at ng OsLOX3 knockout lines. Ang resultang ito ay katulad sa FTIR, ang mga spectra ay maihahambing sa isa’t isa nagmumungkahi ng walang malaking pagbabago sa pangkalahatang thermal stability o maramihang pagbabago sa kumposisyon functional group nito. Ngunit ang second-derivative spectra ay sinailalim sa principal component analysis (PCA) at napagalamang may pagpapangkat mula sa control at OsLOX3 knockout lines sa IRRI154 at walang separasyon na naobserbahan sa Samba Mahsuri. Ang LC-MS ay nagpakita ng malaking pagbabago sa mga metabolites na kaugnay sa oxylipin at iba pang mga metabolic pathways, kasama rin dito ang pagtaas ng oleic acid (C18:1). Sa kabuuan, nagpapakita ang mga resulta sa pagaaral na ito ng mas malalim na pag-unawa sa papel ng OsLOX3 sa lipid oxidation at sa maaring potensyal na maibibigay nito sa pagpapahaba ng pag-imbak sa bigas.

Abstract Format

html

Language

English

Format

Electronic

Keywords

Rice; Rancidity; Linoleic acid

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Embargo Period

12-12-2028

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Available for download on Tuesday, December 12, 2028

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