Bertsch Pascal, Etter Danai, Fischer Peter
Institute of Food Nutrition and Health, ETH Zurich, 8092 Zurich, Switzerland.
Food Funct. 2021 May 11;12(9):4015-4020. doi: 10.1039/d1fo00630d.
Kombucha is a traditional beverage obtained by the fermentation of sugared tea by a symbiotic culture of bacteria and yeast which has recently re-emerged as a popular lifestyle product with potential health benefits. The characteristic feature of kombucha is the formation of a cellulosic biofilm due to the excretion of bacterial cellulose with high purity and crystallinity. Despite the growing industrial and technological interest in kombucha, current characterization techniques rely on the periodic sampling of tea broth or biofilm and ex situ analysis of its biochemical or microbial composition. Here, we use interfacial shear rheology (ISR) for the transient in situ determination of kombucha biofilm growth directly at the interface. ISR revealed that kombucha biofilm formation is a two step process with clearly distinguishable growth phases. The first phase can be attributed to the initial adsorption of bacteria at the air-water interface and shows great variability, probably due to varying bacteria content and composition. The second phase is initiated by bacterial cellulose excretion and shows astonishing reproducibility regarding onset and final mechanical properties. Hence, ISR qualifies as a new in situ characterization technique for kombucha biofilm growth and bacterial cellulose production.
康普茶是一种传统饮品，由糖茶通过细菌和酵母的共生培养发酵而成，最近它作为一种具有潜在健康益处的流行生活方式产品再度兴起。康普茶的特征在于，由于高纯度和结晶度的细菌纤维素的分泌，会形成一种纤维素生物膜。尽管工业界和技术界对康普茶的兴趣日益浓厚，但目前的表征技术依赖于定期采集茶液或生物膜样本，并对其生化或微生物组成进行非原位分析。在此，我们使用界面剪切流变学（ISR）直接在界面处对康普茶生物膜的生长进行瞬态原位测定。ISR表明，康普茶生物膜的形成是一个两步过程，具有明显可区分的生长阶段。第一阶段可归因于细菌在气-水界面的初始吸附，且表现出很大的变异性，这可能是由于细菌含量和组成的不同所致。第二阶段由细菌纤维素的分泌引发，在起始和最终力学性能方面表现出惊人的可重复性。因此，ISR有资格作为一种用于康普茶生物膜生长和细菌纤维素生产的新型原位表征技术。
