Soils, Water and Environment Research Institute, Agricultural Research Center, Giza, 12619, Egypt.
Algal Biotechnology Unit, National Research Centre, Giza, 12622, Egypt.
Environ Sci Pollut Res Int. 2022 Jan;29(2):2588-2597. doi: 10.1007/s11356-021-15758-6. Epub 2021 Aug 9.
In order to improve the economic feasibility and environmental sustainability of microalgal bioethanol production, a nontoxic, copious agricultural waste, sugarcane bagasse aqueous extract (SBAE) was used for cultivating Nannochloropsis oculata microalga (NNO-1 UTEX Culture LB 2164) as potential sources of substitutes for traditional nutrition to reduce the costs in cultivation through acid digestion and enzymatic treatment before being fermented by Saccharomyces cerevisiae (NRRLY-2034). The primary target of this research was to find out the ethanol from hydrolysate of the defatted biomass of N. oculata grown mixotrophically on SBAE and CO as carbon sources. For acid hydrolysis (AH), the highest carbohydrate yield 252.84 mg/g DW has been obtained with 5.0% (v/v) HSO at 121 °C for 15 min for defatted biomass cultivated mixotrophically on sugarcane bagasse aqueous extract (SBAE) regarding 207.41 mg/g DW for defatted biomass cultivated autotrophically (control treatment). Whereas, the highest levels of reducing sugars has been obtained with 4.0% (v/v) HSO 157.47±1.60 mg/g DW for defatted biomass cultivated mixotrophically compared with 135.30 mg/g DW for the defatted control treatment. The combination of acid hydrolysis 2.0% (v/v) HSO followed by enzymatic treatment (AEH) increased the carbohydrate yields to 268.53 mg/g DW for defatted biomass cultivated mixotrophically on SBAE regarding 177.73 mg/g DW for the defatted control treatment. However, the highest levels of reducing sugars have been obtained with 3.0% (v/v) HSO followed by enzyme treatment that gave 232.39±1.77 for defatted biomass cultivated mixotrophically on SBAE and 150.75 mg/g DW for the defatted control treatment. The sugar composition of the polysaccharides showed that glucose was the principal polysaccharide sugar (60.7-62.49%) of N. oculata defatted biomass. Fermentation of the hydrolysates by Saccharomyces cerevisiae for the acid pretreated defatted biomass samples gave ethanol yield of 0.86 g/L (0.062 g/g sugar consumed) for control and 1.17 g/L (0.069 g/g sugar consumed) for SBAE mixotrophic. Whereas, the maximum ethanol yield of 6.17±0.47 g/L (0.26±0.11 g/g sugar consumed) has been obtained with samples from defatted biomass grown mixotrophically (SBAE mixotrophic) pretreated with acid coupled enzyme hydrolysis.
为了提高微藻生物乙醇生产的经济可行性和环境可持续性，使用无毒、丰富的农业废弃物甘蔗渣水提物（SBAE）来培养 Nannochloropsis oculata 微藻（NNO-1 UTEX Culture LB 2164），作为传统营养物的潜在替代品来源，通过酸消化和酶处理降低培养成本，然后用酿酒酵母（NRRLY-2034）发酵。本研究的主要目标是从以 SBAE 和 CO 为碳源的混合营养生长的脱油 N. oculata 的水解物中提取乙醇。对于酸水解（AH），对于以甘蔗渣水提物（SBAE）为碳源的混合营养生长的脱油生物质，用 5.0%（v/v）HSO 在 121°C 下处理 15 分钟，获得最高的碳水化合物产率 252.84 mg/g DW，而对于以 207.41 mg/g DW 为脱油生物质的自养生长（对照处理）。然而，对于以甘蔗渣水提物（SBAE）为碳源的混合营养生长的脱油生物质，用 4.0%（v/v）HSO 获得的还原糖最高水平为 157.47±1.60 mg/g DW，而脱油对照处理的还原糖最高水平为 135.30 mg/g DW。用 2.0%（v/v）HSO 进行酸水解，然后进行酶处理（AEH），可将以 SBAE 为碳源的混合营养生长的脱油生物质的碳水化合物产率提高到 268.53 mg/g DW，而脱油对照处理的碳水化合物产率为 177.73 mg/g DW。然而，用 3.0%（v/v）HSO 进行酸水解，然后进行酶处理，可获得最高的还原糖水平，对于以甘蔗渣水提物（SBAE）为碳源的混合营养生长的脱油生物质，还原糖水平为 232.39±1.77，而脱油对照处理的还原糖水平为 150.75 mg/g DW。多糖的糖组成表明，葡萄糖是 N. oculata 脱油生物质的主要多糖糖（60.7-62.49%）。用酿酒酵母对酸预处理的脱油生物质样品进行水解发酵，得到对照样品的乙醇产量为 0.86 g/L（0.062 g/g 消耗糖），SBAE 混合营养样品的乙醇产量为 1.17 g/L（0.069 g/g 消耗糖）。然而，用酸结合酶水解预处理以 SBAE 为碳源的混合营养生长（SBAE 混合营养）的脱油生物质样品，可获得最大的乙醇产量为 6.17±0.47 g/L（0.26±0.11 g/g 消耗糖）。
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