Bibi Farhana, Yasmin Humaira, Jamal Asif, Al-Harbi Mohammad S, Ahmad Mushtaq, Zafar Muhammad, Ahmad Bashir, Samra Bassem N, Ahmed Atef F, Ali Muhammad Ishtiaq
Department of Microbiology, Quaid-i-Azam University, Islamabad, Pakistan.
Department of Biosciences, COMSATS University Islamabad (CUI), Islamabad, Pakistan.
Saudi J Biol Sci. 2021 Dec;28(12):7595-7606. doi: 10.1016/j.sjbs.2021.10.011. Epub 2021 Oct 11.
Microalgae biomass is considered an important feedstock for biofuels and other bioactive compounds due to its faster growth rate, high biomass production and high biomolecules accumulation over first and second-generation feedstock. This research aimed to maximize the specific growth rate of fresh water green microalgae a member of family under the effect of pH and phosphate concentration to attain enhanced biomass productivity. This study investigates the individual and cumulative effect of phosphate concentration and pH on specific growth characteristics of in autotrophic mode of cultivation for bioethanol production. Central-Composite Design (CCD) strategy and Response Surface Methodology (RSM) was used for the optimization of microalga growth and ethanol production under laboratory conditions. The results showed that high specific growth rate and biomass productivity of 0.342 day and 0.497 g L day respectively, were achieved at high concentration of phosphate (0.115 g L) and pH (9) at 21st day of cultivation. The elemental composition of optimized biomass has shown enhanced elemental accumulation of certain macro (C, O, P) and micronutrients (Na, Mg, Al, K, Ca and Fe) except for nitrogen and sulfur. The Fourier transform infrared spectroscopic analysis has revealed spectral peaks and high absorbance in spectral range of carbohydrates, lipids and proteins, in optimized biomass. The carbohydrates content of optimized biomass was observed as 58%, with 29.3 g L of fermentable sugars after acid catalyzed saccharification. The bioethanol yield was estimated as 51 % g ethanol/g glucose with maximum of 14.9 g/L of bioethanol production. In conclusion, it can be inferred that high specific growth rate and biomass productivity can be achieved by varying levels of phosphate concentration and pH during cultivation of for improved yield of microbial growth, biomass and bioethanol production.
由于微藻生物量生长速度更快、生物质产量高以及与第一代和第二代原料相比生物分子积累量高，因此被认为是生物燃料和其他生物活性化合物的重要原料。本研究旨在在pH值和磷酸盐浓度的影响下，使淡水绿藻（绿藻科的一员）的比生长速率最大化，以提高生物质生产力。本研究调查了磷酸盐浓度和pH值对自养培养模式下用于生物乙醇生产的特定生长特性的单独和累积影响。采用中心复合设计（CCD）策略和响应面方法（RSM）在实验室条件下优化微藻生长和乙醇生产。结果表明，在培养第21天，磷酸盐浓度为0.115 g/L、pH值为9时，分别实现了0.342 d⁻¹的高比生长速率和0.497 g L⁻¹ d⁻¹的生物质生产力。优化生物质的元素组成显示，除氮和硫外，某些常量元素（碳、氧、磷）和微量元素（钠、镁、铝、钾、钙和铁）的元素积累有所增加。傅里叶变换红外光谱分析显示，优化生物质在碳水化合物、脂质和蛋白质的光谱范围内有光谱峰和高吸光度。优化生物质的碳水化合物含量为58%，酸催化糖化后可发酵糖含量为29.3 g/L。生物乙醇产量估计为51% g乙醇/g葡萄糖，最大生物乙醇产量为14.9 g/L。总之，可以推断，在培养过程中通过改变磷酸盐浓度和pH值水平，可以实现高比生长速率和生物质生产力，从而提高微生物生长、生物质和生物乙醇生产的产量。
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