養豬廢水污泥蛋白於低毒性接著材料應用之可行性與機能性研究

Abstract

本研究旨在運用生物性處理技術達成養豬廢水污泥減量與資源化目標，透過篩選具蛋白酶活性的功能性菌株，以分解污泥中有機質並提取可溶性蛋白質（Soluble Sludge Protein, SSP），作為生物性接著劑之原料來源，進一步評估其膠體黏著性能與應用潛力。實驗初期自養豬廢水重力濃縮槽獲得污泥樣本，並成功篩選出具蛋白酶分泌能力之貝萊斯芽孢桿菌（Bacillus velezensis），應用於污泥水解以提高蛋白質提取效率。經條件優化後（培養溫度25 °C、使用超音波清洗機進行污泥震盪預處理及菌液與污泥液體積比為1:2），有效提升蛋白質提取率，並進一步採用中央合成設計法（Central Composite Design, CCD）優化菌株培養配方，獲得最佳條件為檸檬酸鈉2.313 g/L、氯化鎂2.884 g/L、氯化錳0.04 g/L，使蛋白質提取率自2.51%提升至2.69%。所得之SSP與阿拉伯膠（Gum Arabic, GA）及聚丙烯醯胺（Polyacrylamide, PAM）依照不同配方和比例混合製備成複合型生物性接著劑，進行拉脫力測試後發現，以35% GA組別表現最佳，其拉脫力強度達1.402 ± 0.231 MPa，顯著優於市售接著劑（1.1 ± 0.067 MPa）。儘管PAM添加可改善膠體之分散性與流動性，惟過量添加可能包覆官能基點位，抑制與基材間的有效鍵結，導致接著力下降。此外，當SSP添加比例過高，例如GA:(PAM + SSP) = 1:2～1:4時，黏著強度明顯下降至低於0.2 MPa。掃描式電子顯微鏡（SEM）觀察結果指出，高濃度GA可促進膠體內部鍵結強化，形成緻密立體結構網絡；反之，添加PAM與SSP比例過高則使結構趨於破碎和平坦，降低整體接著強度。傅立葉轉換紅外光譜（FTIR）分析顯示，在GA:(PAM + SSP) = 1:1配方中醯胺基含量最高（1.033 ± 0.037），推測此結果來自GA與PAM間之交互作用。然而，該組雖具較高官能基含量，卻未顯著提升拉脫力強度，顯示醯胺基含量與接著力間可能無明確線性關聯。另外，針對接著強度較低之配方，進一步於GA:(PAM + SSP) = 1:4 組別中分別添加10%與20%甘油，進行拉脫力與剪切力強度測試。雖拉脫力無明顯提升，但添加10%甘油者之剪切強度顯著提高至0.09 ± 0.01 MPa。應用於掛鉤背膠測試時，該配方可承重3 kg，並穩定維持至少一週，展現良好實用潛力。整體而言，本研究不僅成功開發以廢棄物資源化為基礎之環保型膠體材料，亦證實其於結構黏著領域之應用潛力，未來可持續優化其物化特性與結構穩定性，以替代傳統化學接著劑，兼顧環境永續、安全性與功能性，為發展綠色材料與循環經濟提供新方向。

This study aimed to achieve simultaneous sludge reduction and resource recovery from pig wastewater sludge through the application of biological treatment technologies. By isolating functional microbial strains with proteolytic activity, organic matter in the sludge was enzymatically hydrolyzed to extract sludge soluble protein (SSP), which was subsequently utilized as a bio-based raw material for adhesive development, in order to further evaluate its colloidal adhesion properties and application potential. Sludge samples were collected from a gravity thickener in a pig wastewater treatment system, from which Bacillus velezensis, a protease-secreting strain, was successfully isolated and employed for sludge hydrolysis. Optimization of hydrolysis conditions—including cultivation at 25 °C, ultrasonic pretreatment of the sludge, and a bacterial suspension-to-sludge volume ratio of 1:2—significantly enhanced protein extraction efficiency. Further refinement using central composite design (CCD) identified the optimal culture medium composition as 2.313 g/L sodium citrate, 2.884 g/L magnesium chloride, and 0.04 g/L manganese chloride, resulting in an increase in protein extraction efficiency from 2.51% to 2.69%. The extracted SSP was then combined with gum arabic (GA) and polyacrylamide (PAM) at various ratios to formulate composite bio-adhesives. Among all tested formulations, the one containing 35% GA exhibited the highest pull-off strength (1.402 ± 0.231 MPa), significantly exceeding that of a commercial adhesive (1.1 ± 0.067 MPa). Although PAM contributed to improved colloidal dispersion and flowability, its excessive addition likely led to the encapsulation of functional groups, thereby impeding effective bonding with the substrate and reducing overall adhesive performance. Similarly, increasing the proportion of SSP—particularly in GA:(PAM + SSP) ratios of 1:2 to 1:4—resulted in a notable decline in bonding strength (< 0.2 MPa). Morphological analysis via scanning electron microscopy (SEM) revealed that higher GA content promoted the formation of compact, three-dimensional network structures through enhanced internal cohesion. In contrast, excessive addition of PAM and SSP yielded flattened, fractured morphologies with weakened structural integrity. Fourier-transform infrared spectroscopy (FTIR) indicated the highest amide group intensity (1.033 ± 0.037) in the GA:(PAM + SSP) = 1:1 formulation, likely attributable to interactions between GA and PAM. However, this did not translate into a corresponding increase in adhesive strength, suggesting a non-linear or indirect relationship between amide content and mechanical performance. To enhance the properties of lower-strength formulations, glycerol was incorporated at 10% and 20% into the GA:(PAM + SSP) = 1:4 system. Although pull-off force remained largely unchanged, the addition of 10% glycerol significantly improved shear strength, reaching 0.09 ± 0.01 MPa. When applied in a hook-and-loop adhesion test, this formulation was able to sustain a 3 kg load for over one week, demonstrating strong practical applicability. In conclusion, this study successfully developed a sustainable, waste-derived bio-based adhesive with considerable potential for use in structural bonding applications. The findings highlight the viability of converting sludge-derived proteins into functional adhesive materials and underscore their promise as eco-friendly alternatives to conventional chemical adhesives, contributing meaningfully to the advancement of green materials and circular economy practices.