Data_Sheet_1_Fungal Growth in Batch Culture – What We Could Benefit If We Start Looking Closer.docx

Since filamentous fungi rapidly adjust their metabolic properties to environmental changes, a rigorous standardization and characterization of cultivation conditions is necessary to obtain meaningful and reproducible results. In batch cultures, which are commonly characterized according to the classical growth curve in textbooks (i.e., lag, exponential, stationary, and declining phase), this is of special difficulty. Although various studies in literature report atypically shaped growth curves of filamentous fungi in batch culture, systematic investigations on this topic are scarce and deviations are barely mentioned in textbooks. Summarizing approximately a decade of observations of growth characteristics from bioreactor batch grown filamentous fungi – in particular two strains (CBS123.823 and CBS123.824) of Penicillium ochrochloron – we demonstrate with a series of highly standardized bioreactor batch culture experiments that the classical growth curve failed to describe growth dynamics of the studied fungi in this work. The nature of the first exhausted nutrient was of remarkable importance for the resulting shape of the growth curve. In all experiments, online respirometry proved to be a powerful tool to distinguish growth phases and revealed more physiological states than expected from the mere biomass curve. In this respect we discuss why “atypical” shaped growth curves often remain unrecognized and that they might be the rule rather than the exception. Acknowledging the importance of the correct presentation of this complex topic in textbooks, we also propose a modified growth curve scheme to sensitize students for potential alternative shaped growth curves.

由于丝状真菌可快速响应环境变化以调整其代谢特性，因此为获取具有科学意义且可重复的实验结果，必须对培养条件开展严格的标准化操作与表征分析。在通常依据教科书中经典生长曲线（即迟缓期、对数生长期、稳定期与衰亡期）进行特性表征的分批培养体系中，这类标准化工作尤为困难。尽管已有诸多文献报道了丝状真菌在分批培养中呈现非典型生长曲线的现象，但针对该主题的系统性研究仍较为匮乏，且教科书中几乎未提及此类生长偏差。本文总结了近十年来针对生物反应器分批培养的丝状真菌生长特性的观察结果，尤其针对两株赭绿青霉（Penicillium ochrochloron）菌株CBS123.823与CBS123.824，并通过一系列高度标准化的生物反应器分批培养实验证明：经典生长曲线无法准确描述本研究中受试真菌的生长动态。首个被耗尽的营养物质对生长曲线的最终形态具有显著影响。在所有实验中，在线呼吸测定法（online respirometry）均被证明是区分生长阶段的有力工具，其揭示的生理状态数量远超仅通过生物量曲线所能观测到的结果。就此而言，本文讨论了为何“非典型”生长曲线往往难以被识别，并指出这类非典型曲线或许才是常态而非例外。考虑到教科书中准确呈现这一复杂主题的重要性，本文还提出了一种改良版生长曲线模型，以帮助学生认识潜在的非典型生长曲线形态。