Table1_Impact of the Purification Process on the Spray-Drying Performances of the Three Families of Lipopeptide Biosurfactant Produced by Bacillus subtilis.pdf

Lipopeptides produced by Bacillus subtilis display many activities (surfactant, antimicrobial, and antitumoral), which make them interesting compounds with a wide range of applications. During the past years, several processes have been developed to enable their production and purification with suitable yield and purity. The already implemented processes mainly end with a critical drying step, which is currently achieved by freeze-drying. In this study, the possibility to replace this freeze-drying step with a spray-drying one, more suited to industrial applications, was analyzed. After evaluating their thermal resistance, we have developed a spray-drying methodology applicable for the three lipopeptides families produced by B. subtilis, i.e., surfactin, mycosubtilin (iturin family), and plipastatin (fengycin family). For each lipopeptide, the spray-drying procedure was applied at three steps of the purification process by ultrafiltration (supernatant, diafiltered solution, and pre-purified fraction). The analysis of the activities of each spray-dried lipopeptide showed that this drying method is not decreasing its antimicrobial and biosurfactant properties. The methodology developed in this study enabled for the first time the spray-drying of surfactin, without adjuvants’ addition and regardless of the purification step considered. In the case of fengycin and mycosubtilin, only diafiltered solution and purified fraction could be successfully spray-dried without the addition of adjuvant. Maltodextrin addition was also investigated as the solution for the direct drying of supernatant. As expected, the performances of the spray-drying step and the purity of the powder obtained are highly related to the purification step at which the product was dried. Interestingly, the impact of mycosubtilin concentration on spray-drying yield was also evidenced.

枯草芽孢杆菌（Bacillus subtilis）所产生的脂肽（lipopeptides）具备多种生物活性，包括表面活性剂活性、抗菌活性与抗肿瘤活性，使其成为一类应用前景广阔的高价值化合物。近年来，学界已开发出多种工艺可实现脂肽的生产与纯化，并获得符合要求的收率与纯度。当前已落地的生产工艺大多以关键干燥步骤作为最终环节，目前该环节普遍采用冷冻干燥（freeze-drying）技术完成。本研究针对更适配工业化应用场景的喷雾干燥（spray-drying）技术替代冷冻干燥步骤的可行性展开了分析。在评估脂肽的耐热性后，本研究开发出一套适用于枯草芽孢杆菌所产生的三类脂肽家族的喷雾干燥工艺，涵盖表面活性素（surfactin）、霉孢菌素（伊枯草菌素（iturin）家族）以及脂肽霉素（芬枯草菌素（fengycin）家族）。针对每一类脂肽，本研究分别在超滤（ultrafiltration）纯化流程的三个阶段开展喷雾干燥实验，即发酵上清液、渗滤液与预纯化组分。对经喷雾干燥处理的脂肽的活性分析结果表明，该干燥工艺并未降低其抗菌活性与生物表面活性剂活性。本研究所开发的工艺首次实现了无需添加助剂、且不受纯化阶段限制的表面活性素喷雾干燥。而对于芬枯草菌素与霉孢菌素而言，仅渗滤液与预纯化组分可在不添加助剂的前提下实现成功的喷雾干燥。本研究同时考察了添加麦芽糊精（maltodextrin）作为助剂，以实现直接干燥发酵上清液的可行性。正如预期，喷雾干燥环节的工艺性能与所得粉末的纯度，与产品干燥时所处的纯化阶段高度相关。值得注意的是，本研究同时证实了霉孢菌素浓度对喷雾干燥收率的影响。