Enzymatic Conversion of Sweetpotato Starch Residue into New Food Materials

从甘薯(SP)和木薯(CA)等热带根茎作物中生产淀粉会产生相当数量的淀粉残留物作为副产品。这种残渣含有丰富的细胞壁材料(CWM)，这使其成为潜在的膳食纤维来源。本研究对SP、CA和马铃薯(PO)三种根茎作物的淀粉残渣制得的CWMS的糖组成进行了表征，并尝试用酶法将其转化为可溶性膳食纤维。对于相对不溶的样品，需要先用12M的H_2SO_4进行预处理，然后再用1M的H_2SO_4进行完全水解。对于单糖的分析，使用CarboPac PA10柱而不是PA1柱的HPAEC-PAD方法得到了可靠的糖组成。利用这种分析方法，测定了CWMS及其多糖组分的糖组成。在…多糖组分中作用更多的是，只有在半纤维素组分中，糖组成，特别是半乳糖含量在三种根茎作物之间存在显著差异。这是首次报道水煤浆的糖组成。为了将水煤浆转化为可溶性膳食纤维，从土壤中分离到一株产生水煤浆降解酶的细菌，芽孢杆菌。M4，并用其培养滤液中的粗酶溶液溶解残留物。芽孢杆菌属已发现M4能分泌多聚半乳糖醛酸裂解酶和多聚糖解聚酶，尤其是阿拉伯聚糖酶，而纤维素酶活性几乎不存在。对三种根茎作物水煤浆的溶解产物进行了糖分分析，发现其主要由半乳糖醛酸类物质和果胶组分中常见的中性糖组成，表明M4酶具有原果胶酶活性。用HPAEC-PAD对还原产物进行末端糖分析，确定粗酶的作用方式。结果表明，M4酶攻击原果胶的半乳糖和鼠李半乳糖醛酸基，导致果胶部分的可溶性膳食纤维的释放。较少

The manufacture of starch from tropical rootcrops like sweetpotato (SP) and cassava (CA) produce considerable amounts of starch residue as by-product. This residue is rich in cell wall material (CWM) which makes it a potential source of dietary fiber. This study characterized the CWMs obtained from the starch residue of three rootcrops, SP, CA, and potato (PO) in terms of their sugar composition and attempted to convert them into soluble dietary fiber enzymatically.To characterize the CWMs from the rootcrops, their sugar compositions were analyzed first. For relatively insoluble samples, pretreatment with 12 M H_2SO_4 prior to hydrolysis with 1 M H_2SO_4 was required for complete hydrolysis. For monosaccharide analysis, HPAEC-PAD method with a CarboPac PA10 column, instead of a PA1 column resulted in reliable sugar composition of these samples. Using this method of analysis, the sugar composition of the CWMs and their polysaccharide fractions was determined. Among the polysaccharide fr … More actions, it was only in the hemicellulose fraction where significant differences in the sugar composition, especially in the galactose content were observed among the three rootcrops. This has been the first report on the sugar composition of CA CWM.To convert the CWMs into soluble dietary fiber, a bacteria producing a CWM-degrading enzyme was isolated from soil, Bacillus sp. M4, and the crude enzyme solution from its culture filtrate was used to solubilize the residues. Bacillus sp. M4 has been found to secrete polygalacturonic acid lyase and glycan depolymerase activities especially arabinanase, but cellulase activity was nearly absent. Sugar analysis of the solubilized product from the CWM of the three rootcrops revealed that it is mainly composed of galacturonic acid, and the neutral sugars found commonly in the pectin fraction, suggesting the presence of a protopectinase activity in M4 enzyme. The mode of action of the crude enzyme was determined by terminal sugar analysis using HPAEC-PAD after hydrolysis of the reduced products. Results revealed that M4 enzyme attacked the galactan as well as rhamnogalacturonan moieties of the protopectin, resulting in the release of a soluble dietary fiber of pectin fraction. Less