Effects of agitation on particle-size distribution and enzymatic hydrolysis of pretreated spruce and giant reed.
Effects of agitation on particle-size distribution and enzymatic hydrolysis of pretreated spruce and giant reed.
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DOI：
10.1186/1754-6834-7-77
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发表时间：
2014
影响因子：
6.3
通讯作者：
Lidén G
中科院分区：
文献类型：
--
作者：
Kadić A;Palmqvist B;Lidén G
混合是一个需要能量的过程，以前已经证明会影响酶水解。浓缩的生物质浆料具有高粘度和非牛顿粘度，在这些系统中混合是一项复杂的任务。混合不良会导致质量和/或传热问题，以及酶分布不均匀，这两者都可能导致产量降低。此外，搅拌能量耗散会影响颗粒大小，进而影响酶解。当前工作的目的是具体量化混合对颗粒大小分布（PSD）的影响，并将其与酶水解的变化联系起来。研究了两种不同的材料，即预处理挪威云杉和巨芦苇。在7或13%水不溶性固体（WIS）的纤维负荷下，酶解过程中葡聚糖水解和PSD的变化作为搅拌的函数进行了测量。在WIS含量较高的情况下，搅拌速率对预处理云杉的酶转化有较大影响。而在WIS含量较低时，搅拌对水解几乎没有影响。搅拌对大芦苇在高WIS负荷下的水解有一定影响，但对云杉的影响较小，低WIS负荷下对大芦苇的水解无明显影响。在云杉的情况下，强烈的搅拌明显影响PSD并导致平均粒径的减小，而对于巨芦苇，粒径的减小主要是由酶作用驱动的。然而，搅拌后的酶解速率并没有提高。搅拌对酶解的影响不仅取决于原料，还取决于固体负载。搅拌对不同预处理材料的PSD有不同的影响。减小的平均颗粒直径不能解释云杉在高搅拌条件下水解速率的提高，这一事实表明，在持续高粘度条件下的传质在决定酶解速率方面起着重要作用。
Mixing is an energy demanding process which has been previously shown to affect enzymatic hydrolysis. Concentrated biomass slurries are associated with high and non-Newtonian viscosities and mixing in these systems is a complex task. Poor mixing can lead to mass and/or heat transfer problems as well as inhomogeneous enzyme distribution, both of which can cause possible yield reduction. Furthermore the stirring energy dissipation may impact the particle size which in turn may affect the enzymatic hydrolysis. The objective of the current work was to specifically quantify the effects of mixing on particle-size distribution (PSD) and relate this to changes in the enzymatic hydrolysis. Two rather different materials were investigated, namely pretreated Norway spruce and giant reed. Changes in glucan hydrolysis and PSD were measured as a function of agitation during enzymatic hydrolysis at fiber loadings of 7 or 13% water-insoluble solids (WIS). Enzymatic conversion of pretreated spruce was strongly affected by agitation rates at the higher WIS content. However, at low WIS content the agitation had almost no effect on hydrolysis. There was some effect of agitation on the hydrolysis of giant reed at high WIS loading, but it was smaller than that for spruce, and there was no measurable effect at low WIS loading. In the case of spruce, intense agitation clearly affected the PSD and resulted in a reduced mean particle size, whereas for giant reed the decrease in particle size was mainly driven by enzymatic action. However, the rate of enzymatic hydrolysis was not increased after size reduction by agitation. The impact of agitation on the enzymatic hydrolysis clearly depends not only on feedstock but also on the solids loading. Agitation was found to affect the PSD differently for the examined pretreated materials spruce and giant reed. The fact that the reduced mean particle diameter could not explain the enhanced hydrolysis rates found for spruce at an elevated agitation suggests that mass transfer at sustained high viscosities plays an important role in determining the rate of enzymatic hydrolysis.
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