Cottonseeds are classified as glanded or glandless seeds depending on the presence or absence of pigment glands which contain toxic gossypol. Glanded cottonseeds from the most widely grown cotton plant compose of approximately 10% linters, 40% hulls and 50% kernels which contain about 35% of oil and 40% of protein. After oil extraction, commercial cottonseed meal from glanded seeds contains up to 1% residual gossypol, which limits its use of meals primarily to feed ruminants. Gossypol can bind to proteins and makes it more difficult to recover concentrated protein fractions from the meal free of gossypol. Glandless seeds do not contain pigment glands and have only trace amount of gossypol which may be useful for potential utilization of the protein as a food ingredient or as a feed for non-ruminant animals. Developing improved extraction techniques for cottonseed proteins would provide additional markets for the cottonseed meal and improve overall profitability of the seed. The objective of this study was to compare and identify protein components in glanded and glandless cottonseeds. The seeds were treated with liquid nitrogen before being grounded into fine powder. The powders were suspended in aqueous buffer and blended again, resulted in homogenates with yellowish and brown colors from glanded and glandless seeds, respectively. After centrifugation, the top lipid layers were scooped and the middle layer contained proteins. The protein layers were precipitated with ammonium sulfate followed by centrifugation. Protein pellet were suspended in a buffer and desalted with centrifugal concentrator. SDS-PAGE showed that a similar pattern of polypeptide bands from both types of seeds. However, mass spectrometry identified numerous of proteins in both cottonseeds but glandless seeds contained more proteins than glanded seeds. This study suggests that the lack of gossypol gland in glandless seeds altered its protein compositions in the seeds.

Characterization and identification of protein components in glanded and glandless cottonseeds

255th National Meeting (2018)

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