This study evaluated the use of biomass of Chlorella minutissima grown in 40-L photobioreactors using a Guillard f/2 biomass at over 80% moisture content as feedstock to produce ethyl esters. The study design investigated the influence of acid catalyst type (HCl or H₂SO₄) and concentration (0.3 or 0.6 mol L⁻¹), co-solvent to ethanol ratio (1:10 or 1:5 v/v), and acyl acceptor to biomass ratio (25 mL g⁻¹ or 50 mL g⁻¹) on ester yield and conversion. An L₈ Taguchi design was used to evaluate the influence of the factors, demonstrating a range of conversion ranging from 37 to 98%. Furthermore, the effects of reaction conditions on the residual biomass were assessed by measuring the concentration of acid-labile carbohydrates, which could be utilized in integrated sugar- and lipid-based algal refineries. It was found that in situ transesterification using HCl can provide easily accessible and fermentable carbohydrates at concentrations of about 32 wt% in residual biomass. In this sense, the findings of this study demonstrate a further step in the integration of microalgae biomass in the development of liquid-fuel biorefineries.

Graphical abstract

中文翻译：

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用于原位生物柴油生产和富含不稳定碳水化合物的残留生物质的高湿小球藻生物质

本研究评估了在 40 升光生物反应器中生长的微小小球藻生物质的使用，该反应器使用含水量超过 80% 的 Guillard f/2 生物质作为生产乙酯的原料。研究设计调查了酸催化剂类型（HCl 或 H ₂ SO ₄）和浓度（0.3 或 0.6 mol L ^-1）、共溶剂与乙醇的比例（1:10 或 1:5 v/v）以及酰基受体与生物质的比率（25 mL g ^-1或 50 mL g ^-1）对酯产率和转化率的影响。安升₈田口设计用于评估这些因素的影响，展示了从 37% 到 98% 的转换范围。此外，通过测量酸不稳定碳水化合物的浓度来评估反应条件对残留生物质的影响，这些碳水化合物可用于基于糖和脂的综合藻类精炼厂。发现使用 HCl 的原位酯交换可以在残余生物质中以约 32 wt% 的浓度提供易于获取和可发酵的碳水化合物。从这个意义上说，这项研究的结果表明，微藻生物质在液体燃料生物精炼厂的发展中又迈进了一步。

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