Garcia-Fernandez Nuria, Hassan Ashraf, Anand Sanjeev
Department of Dairy and Food Science, Midwest Dairy and Food Research Center, South Dakota State University, Brookings 57007.
JDS Commun. 2021 Mar 12;2(3):104-109. doi: 10.3168/jdsc.2020-0041. eCollection 2021 May.
Two different cheese starter cultures producing exopolysaccharides (EPS: strain ST3534 and ssp. strain JFR+) and their isogenic EPS-negative (EPS: strain ST5842 and ssp. strain JFR-) variants were used to study the attachment of bacterial cells in the absence of growth (at 4°C) and the resultant biofilm formation on reverse osmosis membranes (at 30 or 35°C). We used M17 broth and a 10% solution of whey protein concentrate (with 35% protein) as growth media for biofilm development under static conditions. As expected, ST3534 (EPS) showed significantly greater cell counts within biofilms than ST5842 (EPS). In the absence of growth, however, cells of these 2 isogenic strains attached to the membrane in similar numbers. In contrast, JFR+ counts were significantly lower than those of JFR- under all conditions. These findings indicate that the EPS produced by may play a greater role in building up the 3-dimensional structure of the biofilm, rather than only assisting during initial attachment of the cells to the membrane, whereas the EPS produced by ssp. hampered both initial attachment to the membrane and biofilm formation. Although no differences were observed in the surface charge of the cells between the 2 EPS-producing cultures, surface hydrophobicity was associated with the different adhesive properties of these microorganisms. In conclusion, our results exclude the hypothesis that all EPS-producing starter cultures have an advantage in regard to their ability to form biofilm on membrane separation surfaces. In contrast, variations between different EPS, with hydrophobicity being an important influencing feature, modify adhesive behavior to reverse osmosis membranes.
使用两种不同的产生胞外多糖（EPS）的奶酪发酵剂培养物（EPS：菌株ST3534和嗜热栖热放线菌菌株JFR +）及其同基因EPS阴性（EPS：菌株ST5842和嗜热栖热放线菌菌株JFR -）变体，研究在无生长条件下（4°C）细菌细胞的附着以及随后在反渗透膜上（30或35°C）生物膜的形成。我们使用M17肉汤和10％的乳清蛋白浓缩液（含35％蛋白质）溶液作为静态条件下生物膜形成的生长培养基。正如预期的那样，ST3534（EPS）在生物膜中的细胞计数明显高于ST5842（EPS）。然而，在无生长条件下，这两种同基因菌株的细胞以相似数量附着于膜上。相比之下，在所有条件下JFR +的计数均明显低于JFR -。这些发现表明，由ST3534产生的EPS可能在构建生物膜的三维结构中发挥更大作用，而不仅仅是在细胞最初附着于膜的过程中起辅助作用，而嗜热栖热放线菌产生的EPS则阻碍了细胞对膜的最初附着和生物膜的形成。尽管在两种产生EPS的培养物之间未观察到细胞表面电荷的差异，但表面疏水性与这些微生物的不同粘附特性相关。总之，我们的结果排除了所有产生EPS的发酵剂培养物在膜分离表面形成生物膜的能力方面具有优势的假设。相反，不同EPS之间的差异，其中疏水性是一个重要的影响因素，改变了对反渗透膜的粘附行为。
