Abstract

Laccase treatment of phenolic compounds found in lignocellulosic hydrolysates is an alternative to reduce the growth inhibitory effect of these compounds on fermenting microorganisms. In order to determine the main factors that affect the efficiency of this biocatalytic approach, laccase oxidation of individual and mixtures of phenolic compounds was evaluated. Additionally, the effect of phenolic compounds on Saccharomyces cerevisiae cell physiology and their effect on yeast membrane liposome models were evaluated. Trametes versicolor laccase showed complete oxidation of six phenolic compounds, while Agaricus bisporus laccase showed oxidation percentages ranging between 30–100%. High Performance Liquid Chromatography (HPLC) analyses suggested that compounds such as syringic acid, catechol and gallic acid were not completely polymerised after laccase treatment, which could explain the increase of negative effects observed when they were added to S. cerevisiae cultures. Ferulic acid and vanillin oxidation led to a 6.4 and 6.5-fold increase in ethanol production, respectively, compared with the untreated cultures. In phenolic mixtures, chemical interactions between phenolic compounds led to biotransformation of these compounds since different by-products were observed in HPLC chromatograms. Moreover, after laccase treatment, the negative effects of these mixtures were reduced, resulting in an increase in ethanol production yields. No correlation was observed between growth inhibition data, the effect on liposomes and the detoxification efficiencies. Thus, the efficiency of laccase detoxification was not related to the toxicity of the compounds but could be conditioned by the heterogeneity in the chemical structure and properties of these compounds (functional side groups, hydrophobicity, pKa).

摘要

对木质纤维素水解产物中发现的酚类化合物进行漆酶处理是降低这些化合物对发酵微生物生长抑制作用的替代方法。为了确定影响这种生物催化方法效率的主要因素，评估了酚类化合物的个体和混合物的漆酶氧化。此外，评估了酚类化合物对酿酒酵母细胞生理的影响及其对酵母膜脂质体模型的影响。杂色曲霉漆酶显示出六种酚类化合物的完全氧化，而双孢蘑菇漆酶的氧化百分比在30-100％之间。高效液相色谱（HPLC）分析表明，漆酶处理后，丁香酸，儿茶酚和没食子酸等化合物未完全聚合，这可以解释当将它们添加到啤酒酵母中时观察到的负面影响增加。文化。与未处理的培养物相比，阿魏酸和香草醛的氧化分别导致乙醇产量增加6.4倍和6.5倍。在酚类混合物中，酚类化合物之间的化学相互作用导致这些化合物的生物转化，因为在HPLC色谱图中观察到不同的副产物。此外，在漆酶处理后，这些混合物的负面影响得以减轻，从而提高了乙醇的产量。在生长抑制数据，对脂质体的影响和解毒效率之间未观察到相关性。因此，漆酶解毒的效率与化合物的毒性无关，但可以通过这些化合物的化学结构和性质（官能侧基，疏水性，pKa）的异质性来调节。