Food Technology Department-DTA/IRSAT/CNRST, Ouagadougou 03 BP 7047, Burkina Faso.
Int J Food Microbiol. 2013 Mar 1;162(1):114-9. doi: 10.1016/j.ijfoodmicro.2012.12.027. Epub 2013 Jan 7.
Maari is a spontaneously alkaline fermented food condiment made from baobab tree seeds. Due to the spontaneous nature of maari fermentations growth of the opportunistic human pathogen Bacillus cereus is occasionally observed. Bacillus subtilis strains are important for alkaline seed fermentations because of their enzymatic activities contributing to desirable texture, flavor and pH development. Some B. subtilis strains have antimicrobial properties against B. cereus. In the present work, three bacteriocin producing B. subtilis strains (B3, B122 and B222) isolated from maari were tested. The production of antimicrobial activity by the three strains was found to be greatly influenced by the substrate. All three B. subtilis strains produced antimicrobial activity against B. cereus NVH391-98 in BHI broth as determined by the agar well diffusion assay, whereas no antimicrobial activity was detected in whole cooked baobab seeds and in 10% (w/v) grinded baobab seeds. Incorporation of BHI with up to 5% (w/w) grinded baobab seeds enhanced the antimicrobial activity of B. subtilis compared with pure BHI in a strain dependent manner. Incorporation of BHI with 50% (w/w) baobab grinded seeds decreased the antimicrobial activity. Addition of the inorganic salts FeCl₃, MgSO₄ and MnSO₄ has previously been reported to increase bacteriocin production of B. subtilis, but the addition of these salts to 10% (w/v) grinded baobab seed broth did not cause antimicrobial activity. Survival of B. cereus NVH391-98 in co-culture with B. subtilis was tested in BHI broth, 10% (w/v) grinded baobab seed based broth and during baobab seed fermentation to produce maari. B. cereus NVH391-98 grew well in all three substrates in mono-culture. All the 3 B. subtilis strains were able to decrease B. cereus NVH391-98 to levels below the detection limit (<10 CFU/ml) in BHI, but not in baobab seed based substrates, even though the outgrowth of B. cereus NVH391-98 was delayed by up to 40 h. In conclusion, production of antimicrobial activity by the investigated B. subtilis strains is highly substrate-specific and strain-specific. The three B. subtilis strains delayed but did not prevent B. cereus outgrowth during baobab seed fermentations. Maari is produced through mixed microbial population fermentations. B. subtilis co-starter culture candidates originating from maari which are able to prevent pathogen outgrowth remain to be identified.
玛阿里是一种由猴面包树种子制成的自发碱性发酵食品调味料。由于玛阿里发酵的自发性，偶尔会观察到机会性病原体蜡样芽孢杆菌的生长。枯草芽孢杆菌菌株因其对理想质地、风味和 pH 值发展的酶活性而对碱性种子发酵很重要。一些枯草芽孢杆菌菌株对蜡样芽孢杆菌具有抗菌特性。在本工作中，从玛阿里中分离出的三株产细菌素的枯草芽孢杆菌（B3、B122 和 B222）进行了测试。发现三株枯草芽孢杆菌的抑菌活性受基质的影响很大。通过琼脂孔扩散法测定，三株枯草芽孢杆菌均能在 BHI 肉汤中对蜡样芽孢杆菌 NVH391-98 产生抗菌活性，而在全熟猴面包种子和 10%（w/v）磨碎的猴面包种子中未检测到抗菌活性。以高达 5%（w/w）的磨碎猴面包种子与 BHI 混合，以菌株依赖的方式增强了枯草芽孢杆菌的抗菌活性，而与纯 BHI 相比。将 BHI 与 50%（w/w）的磨碎猴面包种子混合会降低抗菌活性。先前有报道称，添加三氯化铁、硫酸镁和硫酸锰等无机盐可增加枯草芽孢杆菌细菌素的产生，但在 10%（w/v）磨碎猴面包种子肉汤中添加这些盐不会引起抗菌活性。在 BHI 肉汤、10%（w/v）磨碎猴面包种子基培养基和猴面包种子发酵过程中测试了蜡样芽孢杆菌 NVH391-98 在与枯草芽孢杆菌共培养中的存活情况，以生产玛阿里。蜡样芽孢杆菌 NVH391-98 在单培养中均能在所有三种基质中良好生长。所有 3 株枯草芽孢杆菌菌株均能将蜡样芽孢杆菌 NVH391-98 降低至低于检测限（<10 CFU/ml），但在猴面包种子基基质中不能，尽管蜡样芽孢杆菌 NVH391-98 的生长延迟了多达 40 小时。总之，所研究的枯草芽孢杆菌菌株产生抗菌活性具有高度的基质特异性和菌株特异性。三株枯草芽孢杆菌菌株延迟但未能阻止猴面包种子发酵过程中蜡样芽孢杆菌的生长。玛阿里是通过混合微生物种群发酵生产的。仍然需要确定源自玛阿里的能够防止病原体生长的枯草芽孢杆菌共发酵候选物。
