Abstract

Poly-β-hydroxybutyrate (PHB) belonging to the polyhydroxyalkanoates family is a natural polyester used as a biodegradable plastic for various commercial applications. In this study, soil samples from the vegetable oil processing industry were used to screen for PHB-producing bacteria using Sudan black B staining. Among the isolated bacteria, PHB positive PSR-2 isolate was chosen as a potent PHB producer. The phylogenetic tree revealed that the PSR-2 isolate has a high 16S rRNA gene sequence similarity of 99.9% with Bacillus tequilensis. The PHB content of 2.8 ± 0.09 g/L was produced by PSR-2 isolate in 48 h in a nutrient broth medium containing 1% glucose compared to the PHB production of 1.6 ± 0.08% by the reference strain, Bacillus circulans. Taguchi method was used to optimize PHB production using the alkali-pretreated spent mushroom substrate of sugarcane bagasse (SMS-SB) as an additional carbon substrate along with other energy sources. The optimized factors in the contribution of PHB production from the highest- to the lowest-ranking are as follows: alkali-pretreated SMS-SB, glucose, glycerol, peptone, ammonium chloride, and potassium dihydrogen phosphate at 30 ºC, pH 7.0, which resulted in the production of 12.4 ± 0.95 g/L PHB was higher than the predicted value of 11.59 g/L. The synthesized PHB was characterized using Ultraviolet–visible spectrophotometry, Fourier transform infrared spectrometry, differential scanning calorimetry, thermogravimetric analysis, nuclear magnetic resonance spectroscopy, and gas chromatography-mass spectrometry. The results revealed the presence of hydroxyl (–OH), methyl (–CH₃), methine (=CH–), methylene (–CH₂–) and ester carbonyl (>C=O) groups, which confirmed the PHB structure. Thus, alkali-pretreated SMS-SB plays a significant role as an energy substrate for the production of PHB. This gives the knowledge to utilize cost-effective lignocellulosic agro-waste materials as a feedstock for the sustainable production of biodegradable PHB for many biomedical applications.

Graphic Abstract

中文翻译：

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统计数据优化优化的β-羟基丁酸生物利用枯草芽孢杆菌PSR-2消耗的蘑菇底物。

摘要

属于聚羟基链烷酸酯家族的聚-β-羟基丁酸酯（PHB）是一种天然聚酯，可用作可生物降解的塑料，用于各种商业应用。在这项研究中，使用植物油加工业的土壤样品通过苏丹黑B染色来筛选产生PHB的细菌。在分离出的细菌中，PHB阳性PSR-2分离株被选作有效的PHB产生者。系统进化树显示，PSR-2分离株与芽胞杆菌具有很高的16S rRNA基因序列相似性，为99.9％。PSR-2分离物在含有1％葡萄糖的营养肉汤培养基中在48小时内产生的PHB含量为2.8±0.09 g / L，而参考菌株圆形芽孢杆菌的PHB产量为1.6±0.08％。Taguchi方法用于优化PHB的生产，该方法使用经碱预处理的甘蔗渣废蘑菇基质（SMS-SB）作为其他碳基质以及其他能源。从最高到最低的等级，PHB产生的贡献的优化因素如下：在30ºC，pH 7.0的条件下，碱预处理的SMS-SB，葡萄糖，甘油，蛋白ept，氯化铵和磷酸二氢钾结果导致PHB的产量为12.4±0.95 g / L，高于预测值11.59 g / L。使用紫外可见分光光度法，傅立叶变换红外光谱法，差示扫描量热法，热重分析，核磁共振光谱法和气相色谱-质谱法对合成的PHB进行表征。₃），次甲基（= CH–），亚甲基（–CH ₂ –）和酯羰基（> C = O），证实了PHB的结构。因此，碱预处理的SMS-SB作为生产PHB的能量底物发挥着重要作用。这提供了将成本有效的木质纤维素农业废料用作许多生物医学应用中可生物降解PHB可持续生产的原料的知识。

图形摘要