Sage M, Daufin G, Gesan-Guiziou G
Ondéo-Degrémont 87 chemin des rondes, 78310 Croissy sur Seine, France.
J Dairy Sci. 2008 Oct;91(10):4062-74. doi: 10.3168/jds.2007-0931.
Milk fat is considered to be the main limiting component of the kinetics of dairy wastewater anaerobic digestion. The objective of this work was to give a better understanding of the nonelucidated anaerobic degradation steps of milk fat. For that purpose, the kinetics of fat degradation was quantified in comparison with other milk components (lactose, proteins), regarding the milk fat polluting load and structure [globular (native state), triglycerides]. This work confirms that milk fat is degraded after a lag phase of several days, with a maximal degradation rate 2 to 5 times less than the degradation rate of the other milk components. It was shown that (1) the structure of the fat does not influence the limits of its anaerobic degradation; (2) the lag phase before biogas production is mainly due to unsaturated free fatty acids (FFA); and (3) conversion to biogas occurs at a lower rate for saturated than for unsaturated FFA. Therefore, the prehydrolysis of fat, which increases the instantaneous concentration of unsaturated FFA, sharply increases the length of the lag phase with no significant change in the maximal biogas production rate. To reduce the delay imposed in the biogas production, it is necessary to reduce the concentration of unsaturated FFA.
乳脂肪被认为是乳制品废水厌氧消化动力学的主要限制成分。这项工作的目的是更好地理解乳脂肪尚未阐明的厌氧降解步骤。为此，针对乳脂肪的污染负荷和结构[球状（天然状态）、甘油三酯]，与其他乳成分（乳糖、蛋白质）相比，对脂肪降解动力学进行了量化。这项工作证实，乳脂肪在经过几天的延迟期后开始降解，其最大降解速率比其他乳成分的降解速率低2至5倍。结果表明：（1）脂肪的结构不影响其厌氧降解的限度；（2）沼气产生前的延迟期主要归因于不饱和游离脂肪酸（FFA）；（3）饱和FFA转化为沼气的速率低于不饱和FFA。因此，脂肪的预水解会增加不饱和FFA的瞬时浓度，从而大幅增加延迟期的长度，而最大沼气产生速率无显著变化。为减少沼气生产中的延迟，有必要降低不饱和FFA的浓度。
