Physical studies of cell flocculation

本申请描述了一个旨在进一步了解细胞絮凝现象的研究程序。细胞的絮凝或“结块”特性在啤酒和其他发酵过程中很重要。例如，酿造酵母的絮凝特性是酿酒师选择生产菌株时最关心的问题。过度絮凝的菌株可能会阻止完全发酵，而絮凝不良的菌株也可能导致过滤和风味问题。由于絮凝是细胞分离的主要方法，细胞的“结块”特性在各种其他生物技术工业中也很重要。人们普遍认为，酵母絮凝的程度部分是由于存在于酵母细胞壁上的抗体样物质（或酶分子）与邻近酵母细胞上的糖结合，类似于“分子魔术贴（TM）”。细胞絮凝的速率和程度也强烈依赖于酵母悬浮液的液体混合的类型和大小以及它们的细胞大小。最近，我们已经确认了以下几个方面的重要性：1)酵母表面化学；2)酵母周围的麦芽汁或啤酒的化学性质；3)发酵过程中发生的液体混合。计划用计算机模拟酶分子和糖在结合过程中的运动。使用专门的仪器，还计划确定单个酵母细胞的细胞壁特性。此外，将对工业发酵罐的絮凝行为进行比较，以确认实验室发现。此外，我们还计划与其他研究人员合作，继续开发一种微米级的“絮凝芯片”，以测量破坏酵母细胞之间的酶分子-糖键的力。上述研究计划的成功资助将有助于进一步了解细胞如何絮凝。将这些发现推广到其他胶体食品系统将对食品和生物技术工业具有学术、技术和经济价值。

This application describes a research program designed to further understand the phenomenon of cell flocculation.  The flocculation or "clumping" properties of cells are important in beer and other fermentations.  For example, the flocculation characteristics of brewing yeasts are of prime of concern when brewers select production strains.  Excessively flocculent strains may prevent complete fermentations while poorly flocculent strains may also cause filtration and flavour problems.  The "clumping" properties of cell are also important in various other biotechnological industries, as flocculation is a major method of cell separation.  It is generally accepted that the extent of yeast flocculation is due in part of antibody-like substances (or zymolectins) present on the yeast cell wall that bind to sugars on adjacent yeast cells, akin to a 'molecular velcro(TM)'.  The rate and extent of cell flocculation are also strongly dependent on the type and magnitude of fluid mixing of the yeast suspensions as well as their cell size.  Recently, we have confirmed the importance of 1) yeast surface chemistry, 2) the chemical nature of the wort or beer the yeast is surrounded by and 3) the fluid mixing that occurs in fermentation. It is planned to computer model the movement of the zymolectins and the sugars during binding. Using a specialized instrument it is also planned to determine cell wall properties of individual yeast cells. Additionally, a comparison of flocculation behaviour industrial fermenters will be undertaken to confirm laboratory findings. Also, in collaboration other researchers we also plan to continue development of a micron scale "flocculation chip" to measure the force to disrupt zymolectin-sugar bonds between yeast cells. Successful funding of the above research program will permit further understanding of how cells flocculate.  The extrapolation of these findings to other colloidal food systems will be of academic, technical and economic value to the food and biotechnology industries.