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Author: search.filters.author.Roytrakul, Sittiruk

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    Evaluation of yellow mealworm (Tenebrio molitor) larvae protein extract as a cryoprotectant for frozen Pacific white shrimp
    (2026-06-15)
    Kittiphattanabawon, Phanat
    ;
    Sriket, Chodsana
    ;
    Nalinanon, Sitthipong
    ;
    Phaonakrop, Narumon
    ;
    Roytrakul, Sittiruk
    This study evaluated the application of yellow mealworm ( Tenebrio molitor ) larvae protein extract (YMPE) as a clean-label cryoprotectant for frozen Pacific white shrimp ( Litopenaeus vannamei ), with emphasis on its underlying mechanism. Proteomic profiling identified 12 antifreeze protein-like peptides containing conserved ice-binding motifs (TCTxSxxCxxAx), supporting the cryoprotective potential of YMPE. During dose optimization, shrimp treated with 0.5% YMPE exhibited the highest weight gain (5.57%) and lowest freezable water content (59.67%) (P < 0.05). The cryoprotective efficacy of YMPE was further evaluated over five freeze–thaw cycles in comparison with distilled water and mixed phosphate. YMPE significantly mitigated quality deterioration by enhancing water retention, preserving protein functionality (higher Ca<sup>2+</sup>-ATPase activity), and reducing lysosomal enzyme leakage relative to the control (P < 0.05). Microstructural analysis revealed reduced muscle fiber disruption, characterized by fewer inter-fiber gaps. Mechanistically, YMPE may exert cryoprotective effects through a multimodal mechanism involving ice recrystallization inhibition and formation of a protective protein matrix. Although less effective than mixed phosphate, YMPE consistently improved all quality parameters compared with the control. These findings highlight the potential of insect-derived protein extracts as a novel, biologically based alternative to phosphate additives in seafood processing and provide a foundation for future industrial application.
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    Dual-function antimicrobial-antibiofilm peptide hybrid to tackle biofilm-forming Staphylococcus epidermidis
    (2024-12-01)
    Wongchai, Mathira
    ;
    Wongkaewkhiaw, Saharut
    ;
    Kanthawong, Sakawrat
    ;
    Roytrakul, Sittiruk
    ;
    Aunpad, Ratchaneewan
    Background: Due to their resistance and difficulty in treatment, biofilm-associated infections are problematic among hospitalized patients globally and account for 60% of all bacterial infections in humans. Antibiofilm peptides have recently emerged as an alternative treatment since they can be effectively designed and exert a different mode of biofilm inhibition and eradication. Methods: A novel antibiofilm peptide, BiF, was designed from the conserved sequence of 18 α-helical antibiofilm peptides by template-assisted technique and its activity was improved by hybridization with a lipid binding motif (KILRR). Novel antibiofilm peptide derivatives were modified by substituting hydrophobic amino acids at positions 5 or 7, and both, with positively charged lysines (L5K, L7K). These peptide derivatives were tested for antibiofilm and antimicrobial activities against biofilm-forming Staphylococcus epidermidis and multiple other microbes using crystal violet and broth microdilution assays, respectively. To assess their impact on mammalian cells, the toxicity of peptides was determined through hemolysis and cytotoxicity assays. The stability of candidate peptide, BiF2_5K7K, was assessed in human serum and its secondary structure in bacterial membrane-like environments was analyzed using circular dichroism. The action of BiF2_5K7K on planktonic S. epidermidis and its effect on biofilm cell viability were assessed via viable counting assays. Its biofilm inhibition mechanism was investigated through confocal laser scanning microscopy and transcription analysis. Additionally, its ability to eradicate mature biofilms was examined using colony counting. Finally, a preliminary evaluation involved coating a catheter with BiF2_5K7K to assess its preventive efficacy against S. epidermidis biofilm formation on the catheter and its surrounding area. Results: BiF2_5K7K, the modified antibiofilm peptide, exhibited dose-dependent antibiofilm activity against S. epidermidis. It inhibited biofilm formation at subinhibitory concentrations by altering S. epidermidis extracellular polysaccharide production and quorum-sensing gene expression. Additionally, it exhibited broad-spectrum antimicrobial activity and no significant hemolysis or toxicity against mammalian cell lines was observed. Its activity is retained when exposed to human serum. In bacterial membrane-like environments, this peptide formed an α-helix amphipathic structure. Within 4 h, a reduction in the number of S. epidermidis colonies was observed, demonstrating the fast action of this peptide. As a preliminary test, a BiF2_5K7K-coated catheter was able to prevent the development of S. epidermidis biofilm both on the catheter surface and in its surrounding area. Conclusions: Due to the safety and effectiveness of BiF2_5K7K, we suggest that this peptide be further developed to combat biofilm infections, particularly those of biofilm-forming S. epidermidis.
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    Novel Small Antimicrobial Peptides Extracted from Agricultural Wastes Act against Phytopathogens but Not Rhizobacteria
    (2022-08-01)
    Ditsawanon, Thitiporn
    ;
    Roytrakul, Sittiruk
    ;
    Phaonakrop, Narumon
    ;
    Charoenlappanit, Sawanya
    ;
    Thaisakun, Siriwan
    Nonedible materials such as agricultural wastes can serve as sources of antimicrobial peptides (AMPs) effective against bacterial plant pathogens. In this study, thirteen agricultural samples were collected and their protein hydrolysates obtained using pepsin. Peptides smaller than 3 kDa were purified by reverse-phase chromatography, cation exchange chromatography, and pI-based fractionation and tested for activity against plant pathogenic bacteria at each step. Active peptides were then analyzed for putative mechanisms using nanoLC–MS/MS and the Mascot program. Ultimately, eight candidate peptides originating from bagasse were selected and chemically synthesized for a comparative study of growth inhibition in plant pathogenic bacteria and plant growth-promoting rhizobacteria (PGPRs). Three synthesized peptides exhibited a potent activity against plant pathogenic bacteria while also supporting the growth of PGPRs. Proteomics analysis revealed the peptides PQLAVF (Pro-Gln-Leu-Ala-Val-Phe) and MDRFL (Met-Asp-Arg-Phe-Leu) to act against Xanthomonas oryzae pv. oryzae via membrane-active mechanisms, while peptide VQLMNSL (Val-Gln-Leu-Met-Asn-Ser-Leu) acted against Pectobacterium carotovorum and Agrobacterium rhizogenes through intracellular-active mechanisms. Further study remains necessary to customize peptides by amino acid substitution not only for a higher effective activity against these and other critical pathogens, but also for a higher stability of peptides in critical condition when applied in industrial processes in the future.