Reppke Manfred J, Gerstner Rebecca, Windeisen-Holzhauser Elisabeth, Richter Klaus, Benz J Philipp
Professorship of Fungal Biotechnology in Wood Science, Holzforschung München (HFM), TUM School of Life Sciences, Technical University of Munich, Hans-Carl-von-Carlowitz-Platz 2, 85354, Freising, Germany.
Chair of Wood Science, Holzforschung München (HFM), TUM School of Life Sciences, Technical University of Munich, Winzererstr. 45, 80797, Munich, Germany.
Fungal Biol Biotechnol. 2022 May 23;9(1):10. doi: 10.1186/s40694-022-00141-y.
The mechanical drying of wood chips is an innovative method that improves the heating value of sawmill by-products in an energy-efficient continuous process. The liquid that comes out of the wood chips as press water (PW), however, contains a variety of undissolved as well as dissolved organic substances. The disposal of the PW as wastewater would generate additional costs due to its high organic load, offsetting the benefits in energy costs associated with the enhanced heating value of the wood chips. Our research explored if the organic load in PW could be utilized as a substrate by cellulolytic filamentous fungi. Hence, using the industrially relevant Ascomycete Trichoderma reesei RUT-C30 as well as several Basidiomycete wood-rotting fungi, we examined the potential of press water obtained from Douglas-fir wood chips to be used in the growth and enzyme production media.
The addition of PW supernatant to liquid cultures of T. reesei RUT-C30 resulted in a significant enhancement of the endoglucanase and endoxylanase activities with a substantially shortened lag-phase. A partial replacement of Ca, Mg, K, as well as a complete replacement of Fe, Mn, Zn by supplementing PW of the liquid media was achieved without negative effects on enzyme production. Concentrations of PW above 50% showed no adverse effects regarding the achievable endoglucanase activity but affected the endoxylanase activity to some extent. Exploring the enhancing potential of several individual PW components after chemical analysis revealed that the observed lag-phase reduction of T. reesei RUT-C30 was not caused by the dissolved sugars and ions, nor the wood particles in the PW sediment, suggesting that other, so far non-identified, compounds are responsible. However, also the growth rate of several basidiomycetes was significantly enhanced by the supplementation of raw PW to the agar medium. Moreover, their cultivation in liquid cultures reduced the turbidity of the PW substantially.
PW was identified as a suitable media supplement for lignocellulolytic fungi, including the cellulase and xylanase producer T. reesei RUT-C30 and several wood-degrading basidiomycetes. The possibility to replace several minerals, trace elements and an equal volume of fresh water in liquid media with PW and the ability of fungal mycelia to filter out the suspended solids is a promising way to combine biological wastewater treatment with value-adding biotechnological applications.
木片的机械干燥是一种创新方法，可通过节能的连续工艺提高锯木厂副产品的热值。然而，作为压榨水（PW）从木片中流出的液体含有各种未溶解以及溶解的有机物质。由于其高有机负荷，将PW作为废水处理会产生额外成本，抵消了与木片热值提高相关的能源成本效益。我们的研究探讨了PW中的有机负荷是否可被纤维素分解丝状真菌用作底物。因此，我们使用工业上相关的子囊菌里氏木霉RUT-C30以及几种担子菌木腐真菌，研究了从花旗松木片中获得的压榨水用于生长和酶生产培养基的潜力。
将PW上清液添加到里氏木霉RUT-C30的液体培养物中，导致内切葡聚糖酶和内切木聚糖酶活性显著提高，滞后期大幅缩短。通过补充液体培养基的PW，实现了部分替代Ca、Mg、K以及完全替代Fe、Mn、Zn，且对酶生产没有负面影响。高于50%的PW浓度对可达到的内切葡聚糖酶活性没有不利影响，但在一定程度上影响了内切木聚糖酶活性。化学分析后探索几种单个PW成分的增强潜力表明，观察到的里氏木霉RUT-C30滞后期减少不是由溶解的糖和离子，也不是由PW沉淀物中的木颗粒引起的，这表明还有其他迄今未鉴定的化合物起作用。然而，向琼脂培养基中添加未处理的PW也显著提高了几种担子菌的生长速率。此外，它们在液体培养物中的培养大大降低了PW的浊度。
PW被确定为木质纤维素分解真菌的合适培养基补充物，包括纤维素酶和木聚糖酶产生菌里氏木霉RUT-C30以及几种木材降解担子菌。用PW替代液体培养基中的几种矿物质、微量元素和等量淡水的可能性以及真菌菌丝体过滤悬浮固体的能力，是将生物废水处理与增值生物技术应用相结合的一种有前景的方法。
