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Subject: search.filters.subject.Alkaline pretreatment

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    High-cell-density culture for recombinant xylanase production and its application in hydrolysis of mild alkaline pretreated rice straw for xylooligosaccharide production
    (2026-08-01)
    Laemthong, Tunyaboon
    ;
    Sukhumsirichart, Wasana
    ;
    Chittapun, Supenya
    ;
    Kongsinkaew, Chatchol
    ;
    Satipattarn, Atikant
    Rice straw is an abundant lignocellulosic residue whose effective utilization requires coordinated enzyme performance and pretreatment conditions. In this study, recombinant xylanase production was integrated with mild alkaline pretreatment to enable efficient conversion of rice straw into xylooligosaccharides (XOS). Recombinant xylanase was produced by Escherichia coli using high-cell-density fed-batch cultivation, achieving a maximum activity of 207.95 U/mL in an enriched synthetic medium. Alkaline pretreatment was optimized using response surface methodology, identifying 6.75% (w/v) biomass loading, 193.17 mM NaOH, and 20 min as conditions that balanced solid recovery with sugar release during subsequent enzymatic hydrolysis. Hydrolysis of the pretreated rice straw yielded 6.13 mg/mL total XOS, mainly xylotriose (X3, 2.73 mg/mL; 44.56%), xylobiose (X2, 2.00 mg/mL; 32.62%), and xylotetraose (X4, 1.02 mg/mL; 16.57%), with only minor amounts of xylose and xylopentaose detected. The combined X2 and X3 fractions accounted for 77.18% of the total XOS. XOS with degrees of polymerization of 2–4 are recognized as effective prebiotics, particularly for beneficial intestinal bacteria such as Bifidobacterium spp. Overall, linking recombinant enzyme production with alkaline pretreatment improved conversion consistency and supported efficient XOS production from rice straw.
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    Enhanced calcium solubility of bio-calcium powder from blackchin tilapia (Sarotherodon melanotheron) bone: Influence of alkaline pretreatment conditions
    (2026-07-01)
    Senphan, Theeraphol
    ;
    Mungmueang, Natthapong
    ;
    Sazedul Hoque, Md
    ;
    Sriket, Chodsana
    ;
    Benjakul, Soottawat
    Bio-calcium powder was prepared from blackchin tilapia ( Sarotherodon melanotheron ) bones, an invasive species by-product from surimi production in Thailand, to evaluate the effects of alkaline pretreatment on bio-calcium properties. Bones were pretreated with NaOH or KOH (1 and 2 M) at a bone-to-solution ratio of 1:10 (w/v) for 2 h, followed by ethanol washing, hydrogen peroxide bleaching, drying, and grinding to obtain bio-calcium powder. The yield on a wet weight basis was 26–28%, with water activity values of 0.33–0.34 measured at room temperature. Among all treatments, 1 M KOH gave the highest yield (28%), calcium content (26.13%), and lightness (L∗ = 88.5). Collagenous proteins and hydroxyapatite were identified by SDS-PAGE and ATR-FTIR, respectively. All bio-calcium samples showed four to five times higher in vitro calcium solubility after simulated gastrointestinal digestion (13.4-17.50%) than calcium carbonate (3.4%). The 2 M treatments exhibited the highest calcium solubility (17.2-17.50%). The 1 M KOH can be used for food fortification due to its high yield and lightness, whereas the 2 M treatments can serve as calcium supplements where higher calcium solubility is required. Blackchin tilapia bone is a potential source for bio-calcium production, with 1 M KOH suitable for food fortification and 2 M treatments more appropriate for applications requiring higher calcium solubility.