Bacillus subtilis Strain ka15: a potent starter isolated from kawal, a fermented condiment

Kawal is a fermented condiment obtained from the natural alkaline fermentation of Senna obtusifolia leaves. The Bacillus strain was isolated from a kawal sample purchased at the Abeche market in Tchad. For genomic DNA extraction, the strain was grown on LB agar. A single colony was selected and grown in LB broth until it reached an optical density of 0.8 at 600 nm (OD600), before being subjected to genomic DNA extraction using the Wizard Genomic DNA Purification kit (Promega). Genomic DNA concentration was determined using an Invitrogen Qubit 4 fluorometer, and sequencing libraries were generated using the Nextera XT DNA library preparation kit (Illumina), according to the manufacturer's instructions. Sequencing was performed using Illumina's NovaSeq platform. The strain is capable of inhibiting the growth of kawal pathogens, including bacteria and molds. It also has probiotic potential and could serve as a starter for controlled kawal fermentation.

卡瓦勒（Kawal）是一种由钝叶决明（Senna obtusifolia）叶片经自然碱性发酵制备而成的发酵调味品。研究人员从乍得阿贝歇市场采购的卡瓦勒样品中分离得到一株芽孢杆菌（Bacillus）菌株。在进行基因组DNA提取前，先将该菌株接种于LB琼脂（LB agar）平板进行培养，挑取单菌落并接种至LB肉汤（LB broth）中扩大培养，待菌液在600 nm波长下的光密度（OD600）达到0.8时，采用Promega公司的Wizard基因组DNA纯化试剂盒完成基因组DNA提取。使用Invitrogen Qubit 4荧光计测定基因组DNA浓度，依照试剂盒制造商的说明书，使用Illumina公司的Nextera XT DNA文库制备试剂盒构建测序文库。随后通过Illumina NovaSeq测序平台完成测序。该菌株能够抑制卡瓦勒相关病原菌（包括细菌与霉菌）的生长，同时具备益生潜能，可作为可控卡瓦勒发酵的起始发酵菌株。