Physical studies of cell flocculation

本申请描述了一项旨在进一步了解细胞絮凝现象的研究计划。例如，啤酒酿造商在选择生产菌株时，啤酒酿造酵母的絮凝特性是最受关注的。过度絮凝的菌株可能会阻止完全发酵，而絮凝能力差的菌株也可能导致过滤和味道问题。此外，在其他各种生物技术产业中，细胞的絮凝特性也很重要。因为絮凝是细胞分离的一种主要方法。人们普遍认为，酵母的絮凝程度是由于酵母细胞壁上的部分抗体样物质(或酵母凝集素)与相邻酵母细胞上的糖结合，类似于分子尼龙搭扣(TM)。此外，细胞絮凝的速度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1)酵母表面化学的重要性，2)酵母周围麦汁或啤酒的化学性质；3)发酵过程中发生的液体混合。计划对酵母凝集素和糖在结合过程中的运动进行计算机模拟。它还计划使用一种专门的仪器来确定单个酵母细胞的细胞壁属性。此外，还将对工业发酵罐的絮凝行为进行比较，以确认实验室结果。此外，在与其他研究人员的合作中，我们还计划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发酵凝集素-糖键的力量。上述研究计划的成功资助将使人们能够进一步了解细胞是如何絮凝的。因此，将这些发现外推到其他胶体食品系统将对食品和生物技术行业具有学术、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.