Animal Nutrition Group, Wageningen University & Research, Wageningen, The Netherlands.
Laboratory of Food Chemistry, Wageningen University & Research, Wageningen, The Netherlands.
J Sci Food Agric. 2019 Jun;99(8):4054-4062. doi: 10.1002/jsfa.9634. Epub 2019 Mar 13.
White rot fungi have been used to improve the nutritive value of lignocellulose for ruminants. In feed analysis, the Van Soest method is widely used to determine the cell wall contents. To assess the reliability of this method (Method A) for determination of cell wall contents in fungal-treated wheat straw, we compared a combined monosaccharide analysis and pyrolysis coupled to gas chromatography with mass spectrometry (Py-GC/MS) (Method B). Ruminal digestibility, measured as in vitro gas production (IVGP), was subsequently used to examine which method explains best the effect of fungal pretreatment on the digestibility of wheat straw.
Both methods differed considerably in the mass recoveries of the individual cell wall components, which changed on how we assess their degradation characteristics. For example, Method B gave a higher degradation of lignin (61.9%), as compared to Method A (33.2%). Method A, however, showed a better correlation of IVGP with the ratio of lignin to total structural carbohydrates, as compared to Method B (Pearson's r of -0.84 versus -0.69). Nevertheless, Method B provides a more accurate quantification of lignin, reflecting its actual modification and degradation. With the information on the lignin structural features, Method B presents a substantial advantage in understanding the underlying mechanisms of lignin breakdown. Both methods, however, could not accurately quantify the cellulose contents - among others, due to interference of fungal biomass.
Method A only accounts for the recalcitrant residue and therefore is more suitable for evaluating ruminal digestibility. Method B allows a more accurate quantification of cell wall, required to understand and better explains the actual modification of the cell wall. The suitability of both methods, therefore, depends on their intended purposes. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
白腐真菌已被用于提高反刍动物木质纤维素的营养价值。在饲料分析中，范索斯特法被广泛用于测定细胞壁含量。为了评估该方法（方法 A）用于测定真菌处理小麦秸秆细胞壁含量的可靠性，我们比较了一种组合的单糖分析和热解与气相色谱-质谱联用（Py-GC/MS）（方法 B）。随后，使用体外产气量（IVGP）来评估哪种方法能最好地解释真菌预处理对小麦秸秆消化率的影响。
两种方法在细胞壁成分的质量回收率上存在显著差异，这取决于我们如何评估它们的降解特性。例如，方法 B 给出了木质素（61.9%）的更高降解率，而方法 A 则为 33.2%。然而，与方法 B 相比，方法 A 显示出与木质素与总结构性碳水化合物的比值对 IVGP 的更好相关性（皮尔逊 r 为-0.84 与-0.69）。然而，方法 B 提供了更准确的木质素定量，反映了其实际修饰和降解。通过木质素结构特征的信息，方法 B 在理解木质素分解的潜在机制方面具有显著优势。然而，这两种方法都不能准确地定量纤维素含量，其中包括由于真菌生物量的干扰。
方法 A 仅考虑了抗降解残留物，因此更适合评估瘤胃消化率。方法 B 允许更准确地定量细胞壁，以理解和更好地解释细胞壁的实际修饰。因此，这两种方法的适用性取决于它们的预期用途。© 2019 作者。《食品科学杂志》由 John Wiley & Sons Ltd 代表化学工业协会出版。
