Department of Microbiology, Faculty of Agriculture, Cairo University, El-Gamaa Street, Giza, 12613, Egypt.
Microb Cell Fact. 2024 Feb 17;23(1):56. doi: 10.1186/s12934-024-02326-z.
Polyhydroxybutyrate (PHB) has emerged as a promising eco-friendly alternative to traditional petrochemical-based plastics. In the present study, we isolated and characterized a new strain of Salinicola salarius, a halophilic bacterium, from the New Suez Canal in Egypt and characterized exclusively as a potential PHB producer. Further genome analysis of the isolated strain, ES021, was conducted to identify and elucidate the genes involved in PHB production.
Different PHB-producing marine bacteria were isolated from the New Suez Canal and characterized as PHB producers. Among the 17 bacterial isolates, Salinicola salarius ES021 strain showed the capability to accumulate the highest amount of PHB. Whole genome analysis was implemented to identify the PHB-related genes in Salinicola salarius ES021 strain. Putative genes were identified that can function as phaCAB genes to produce PHB in this strain. These genes include fadA, fabG, and P3W43_16340 (encoding acyl-CoA thioesterase II) for PHB production from glucose. Additionally, phaJ and fadB were identified as key genes involved in PHB production from fatty acids. Optimization of environmental factors such as shaking rate and incubation temperature, resulted in the highest PHB productivity when growing Salinicola salarius ES021 strain at 30°C on a shaker incubator (110 rpm) for 48 h. To maximize PHB production economically, different raw materials i.e., salted whey and sugarcane molasses were examined as cost-effective carbon sources. The PHB productivity increased two-fold (13.34 g/L) when using molasses (5% sucrose) as a fermentation media. This molasses medium was used to upscale PHB production in a 20 L stirred-tank bioreactor yielding a biomass of 25.12 g/L, and PHB of 12.88 g/L. Furthermore, the produced polymer was confirmed as PHB using Fourier-transform infrared spectroscopy (FTIR), gas chromatography-mass spectroscopy (GC-MS), and nuclear magnetic resonance spectroscopy (NMR) analyses.
Herein, Salinicola salarius ES021 strain was demonstrated as a robust natural producer of PHB from agro-industrial wastes. The detailed genome characterization of the ES021 strain presented in this study identifies potential PHB-related genes. However, further metabolic engineering is warranted to confirm the gene networks required for PHB production in this strain. Overall, this study contributes to the development of sustainable and cost-effective PHB production strategies.
聚羟基丁酸酯（PHB）作为一种有前途的环保型替代传统石油基塑料的材料而出现。在本研究中，我们从埃及新苏伊士运河中分离并鉴定了一株新的嗜盐菌 Salinicola salarius，该菌被专门鉴定为 PHB 的潜在生产菌。对分离株 ES021 进行了进一步的基因组分析，以鉴定和阐明 PHB 生产相关的基因。
从新苏伊士运河中分离出不同的产 PHB 海洋细菌，并鉴定为 PHB 生产菌。在 17 株细菌分离株中，Salinicola salarius ES021 菌株表现出积累 PHB 量最高的能力。对 Salinicola salarius ES021 菌株进行全基因组分析，以鉴定 PHB 相关基因。鉴定出了phaCAB 基因，这些基因可在该菌株中产生 PHB。这些基因包括 fadA、fabG 和 P3W43_16340（编码酰基辅酶 A 硫酯酶 II），用于从葡萄糖生产 PHB。此外，鉴定出了 phaJ 和 fadB 是参与脂肪酸生产 PHB 的关键基因。优化环境因素，如摇床转速和培养温度，当在摇床培养箱中以 30°C 培养 Salinicola salarius ES021 菌株 48 小时时，可获得最高的 PHB 产率（110 rpm）。为了从经济角度最大化 PHB 的产量，研究了不同的原料，即盐水乳清和甘蔗糖蜜作为经济有效的碳源。当使用糖蜜（5%蔗糖）作为发酵培养基时，PHB 的产量增加了两倍（13.34 g/L）。使用该糖蜜培养基在 20 L 搅拌罐生物反应器中扩大 PHB 产量，可得到 25.12 g/L 的生物质和 12.88 g/L 的 PHB。此外，通过傅里叶变换红外光谱（FTIR）、气相色谱-质谱联用（GC-MS）和核磁共振光谱（NMR）分析证实了所产生的聚合物为 PHB。
本研究中，Salinicola salarius ES021 菌株被证明是一种从农业工业废物中生产 PHB 的强大天然生产菌。本研究中对 ES021 菌株的详细基因组特征分析鉴定了潜在的 PHB 相关基因。然而，需要进一步的代谢工程来证实该菌株生产 PHB 所需的基因网络。总的来说，本研究为开发可持续和经济有效的 PHB 生产策略做出了贡献。
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