Velasco S, Arsköld E, Paese M, Grage H, Irastorza A, Rådström P, van Niel E W J
Applied Microbiology, Lund Institute of Technology, Lund University, PO Box 124, SE-221 00 Lund, Sweden.
Int J Food Microbiol. 2006 Oct 1;111(3):252-8. doi: 10.1016/j.ijfoodmicro.2006.06.008. Epub 2006 Jul 18.
Natural exopolysaccharides (EPSs) from food-grade lactic acid bacteria have potential for development and exploitation as food additives and functional food ingredients with both health and economic benefits. In this study, we have examined the physiological capacity of EPS production in Pediococcus parvulus 2.6. EPS formation by P. parvulus 2.6 was found to be linked to biomass yields, provided that glucose was not limiting. Higher biomass yields and EPS productions were obtained when cultures were pH-controlled at pH 5.2. Various compounds have been tested for their influence on growth rate and EPS formation. Of those, only glucose (up to 75 g l(-1)), ethanol (up to 4.9%, w/v) and glycerol (up to 6.6%, w/v) had positive effects on EPS production. EPS production was not directly linked to growth, because its production continued in the stationary phase provided that glucose was present. According to an empirical model, the growth of P. parvulus 2.6 was completely inhibited by 58.9+/-18.1 g l(-1) lactate. Lactate, the sole fermentation product, was suggested to affect growth by chelation of manganese. The organism grew in an apparent linear fashion due to this imposed manganese limitation. This could be overcome by increasing the manganese concentration to at least 2 mg l(-1) in the medium. The excretion of Mn(2+) upon depletion of glucose indicated that maintenance of the high Mn(2+) gradient over the cell membrane is an energy requiring process. EPS production was increased from 0.12 g l(-1) to 4.10 g l(-1) in an improved medium that is based on the results from this study.
食品级乳酸菌产生的天然胞外多糖（EPSs）有开发利用为食品添加剂和功能性食品成分的潜力，兼具健康和经济效益。在本研究中，我们检测了小颗粒四联球菌2.6产生EPS的生理能力。发现小颗粒四联球菌2.6形成EPS与生物量产量有关，前提是葡萄糖不成为限制因素。当培养物在pH 5.2进行pH控制时，可获得更高的生物量产量和EPS产量。已测试了各种化合物对生长速率和EPS形成的影响。其中，只有葡萄糖（高达75 g l⁻¹）、乙醇（高达4.9%，w/v）和甘油（高达6.6%，w/v）对EPS产生有积极影响。EPS产生与生长没有直接联系，因为只要有葡萄糖存在，其产生在稳定期仍会继续。根据一个经验模型，58.9±18.1 g l⁻¹乳酸完全抑制了小颗粒四联球菌2.6的生长。乳酸是唯一的发酵产物，据推测它通过螯合锰来影响生长。由于这种施加的锰限制，该生物体以明显的线性方式生长。通过将培养基中的锰浓度提高到至少2 mg l⁻¹可以克服这一问题。葡萄糖耗尽时Mn²⁺的排泄表明维持细胞膜上高的Mn²⁺梯度是一个需要能量的过程。基于本研究结果的改良培养基中，EPS产量从0.12 g l⁻¹提高到了4.10 g l⁻¹。
