Botany and Microbiology Department, Faculty of Science, Al-Azhar University, Nasr City, Cairo 11884, Egypt.
Al-Azhar Center for Fermentation Biotechnology and Applied Microbiology, Al-Azhar University, Nasr City, Cairo 11884, Egypt.
Int J Biol Macromol. 2021 Nov 1;190:319-332. doi: 10.1016/j.ijbiomac.2021.08.090. Epub 2021 Aug 17.
The demand for the production of biodegradable plastics has significantly increased. Bioplastics have become an essential alternative to the threats of the daily consumable plastics, sourced from fossil fuels, to the environment. Polyhydroxyalkonates (PHAs) are a ubiquitous group of bioderived and biodegradable plastics, however their production is limited by the costs associated mainly with the carbon sources. Herein, this study aims to reduce the PHAs production cost by using a by-product from the dairy industry, i.e., cheese whey (CW), as a sole carbon source. The developed process recruits an aquatic isolate, Bacillus flexus Azu-A2, and is optimized via studying various parameters using the shaking flasks technique. The results showed that the maximum PHA production (0.95 g L) and PHA content (20.96%, w/w), were obtained after incubation period 72 h at 45 °C, 100 rpm agitation rate, 50% CWS concentration, pH 8.5, and 1.0 g L ammonium chloride. Physiochemically, Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectroscopy (GC-MS), nuclear magnetic resonance (NMR), and energy-dispersive X-ray (EDX) techniques, emphasized the type of the extracted PHA as polyhydroxybutyrate (PHB). The thermal properties of PHB were measured using differential scanning calorimetry (DSC), recording melting transition temperature (Tm) at 170.96 °C. Furthermore, a scanning electron microscope (SEM) visualized a homogenous microporous structure for the thin PHB biofilm. In essence, this study highlights the ability of Bacillus flexus Azu-A2 to produce a good yield of highly purified PHB at reduced production cost from dairy CW. Consequently, the current study paves the way for an improved whey management strategy.
对可生物降解塑料的需求大幅增加。生物塑料已成为源自化石燃料的日常消耗性塑料对环境威胁的重要替代品。聚羟基烷酸酯（PHA）是一类普遍存在的生物衍生和可生物降解塑料，但它们的生产受到成本的限制，主要与碳源有关。在此，本研究旨在使用乳制品工业的副产品，即奶酪乳清（CW）作为唯一的碳源来降低 PHA 的生产成本。所开发的工艺利用水生分离菌 Bacillus flexus Azu-A2，并通过使用摇瓶技术研究各种参数进行优化。结果表明，在 45°C、100rpm 搅拌速度、50%CW 浓度、pH8.5 和 1.0g/L 氯化铵的条件下，培养 72 小时后，可获得最大的 PHA 产量（0.95g/L）和 PHA 含量（20.96%，w/w）。傅里叶变换红外光谱（FTIR）、气相色谱-质谱（GC-MS）、核磁共振（NMR）和能量色散 X 射线（EDX）技术强调了提取的 PHA 为聚羟基丁酸酯（PHB）的类型。使用差示扫描量热法（DSC）测量 PHB 的热性能，记录熔融转变温度（Tm）为 170.96°C。此外，扫描电子显微镜（SEM）观察到 PHB 生物膜的均匀微孔结构。总之，本研究强调了 Bacillus flexus Azu-A2 能够从乳制品 CW 以较低的生产成本生产出高产率的高纯度 PHB。因此，本研究为改进乳清管理策略铺平了道路。
