Approaches To The Full Utilization Of Sisal Waste And Functions Of The Active Components

The continuous technology of full use of sisal waste was established in this paper,using the sisal residue after de-fibre as the raw materia.The physicochemical properties and functional characteristics of the active components from sisal waste were also fully analyzed.The study provides a useful reference to solve the problem of environmental pollution of sisal waste and further promote the high value utilization of industrial and agricultural residues.The main results are as follows:1.Firstly,the enriched components with antioxidant activity were separated from sisal waste by ethanol extraction and multi-step classification.Then,the residues of ethanol extraction were treated with acid to obtain sisal soluble dietary fiber（SSDF）.Finally,the remaining solids after acid hydrolysis were collected to obtain the sisal insoluble dietary fiber（SIDF）.Therefore,the approaches to the full utilization of sisal waste were established.2.Petroleum ether fraction（PEF）,ethyl acetate fraction（EAF）,butanol fraction（BF）and water fraction（WF）were received from ethanol extract of sisal waste through classification.The content of each fraction accounted for 4.2%,12.8%,48.7% and 27.4% of the ethanol extract,respectively.The antioxidant activities in vitro using scavenging free radicals were studied,EAF and BF were determined of stronger antioxidant activity.The IC50 of EAF on DPPH free radical,hydroxyl radical and superoxide anion radical were 0.04 mg/mL,0.87 mg/mL and 2.46 mg/m L,respectively.Similarly,The IC50 of BF on DPPH free radical,hydroxyl radical and superoxide anion radical were 0.15 mg/m L,1.04 mg/mL and 4.90 mg/mL,respectively.The contents of total polyphenols,total flavonoids and total saponins were determined,and the main active fractions were separated and identified by HPLC-MS,indicating that the main active components in EAF were polyphenols and flavonoids,while BF was rich in sisal saponin.3.Sisal soluble dietary fiber（SSDF）and sisal insoluble dietary fiber（SIDF）were prepared by acid treatment and solid-liquid separation from the sisal residues after ethanol extraction,and the yield was 9.86% and 58.90%,respectively.It was found that the main component of SSDF was pectic polysaccharide,the esterification degree was measured of 33.4%,the Mw was 116 KDa,and it was confirmed to have good gel properties in the presence of Ca²⁺.Besides,the SIDF was proved to exist inⅠtype crystal structure of cellulose,the average particle size is 233.6 μm,and it was observed that the SIDF displayed honeycomb porous structure with dense network space and smooth surface.4.The study of antioxidant activity in vitro showed that SSDF had the best scavenging effect on hydroxyl radical,and the scavenging rate was 90.4% when the concentration was 5.0 mg/mL.The water-holding capacity,water-binding capacity,water swelling capacity,oil-holding capacity and cation exchange capacity of SIDF were confirmed to improve a lot than sisal residue untreated.In addition,the SIDF was proved to have better effect on nitrite ion adsorption in gastric simulated environment,and the adsorption rate reached 96% within 2 h.In intestinal simulated environment,the SIDF had prominent adsorption on cholesterol and Pb²⁺.The ability of adsorption and diffusion of glucose was also remarkable.In vitro experiments showed that the adsorption process of SIDF on Pb²⁺ was in accordance with the kinetics second order adsorption model and the thermodynamic Langmuir model.The adsorption active sites of sisal waste were hydroxyl,carboxyl and carbonyl groups.The adsorption of Pb²⁺ by SIDF is a single-layer adsorption process,and the main adsorption process was included by physical adsorption,chemical adsorption and ion exchange.