Production and carbon footprint of microbial oil from waste lemon peel extract - supplementary material

Supplementary data and underlying data supporting the finding described in "Production and carbon footprint of microbial oil from waste lemon peel extract". Abstract Background The agricultural sector is one of the leading producers of agro-industrial solid organic waste. This waste is mainly disposed of by incineration or landfilled, representing a huge loss of potential resources, which could be used for the production of high-value chemicals. In this study, a fermentation process for the production of microbial oil from waste lemon extract (LE), an aqueous side stream deriving from waste lemon peel and pulp processing, was developed and assessed for impacts. Microbial oil can have many and diverse applications, from plasticisers in plastic and rubber compounds to moisturizers in cosmetic formulation. Methods and results Characterization of LE revealed that its autoclaving process is effective for increasing the concentration of readily available glucose and fructose, reaching 28.77 ± 0.08 g L-1 and 25.68 ± 0.27 g L-1. Nitrogen content was measured too, revealing a C/N ratio of 85, optimal for triggering lipid accumulation in the selected microbial cell factory. Therefore, the oleaginous yeast Cutaneotrichosporon oleaginosum was cultivated in an unmodified LE-based medium in 2 L bioreactors, resulting in a lipid accumulation of 0.47 ± 0.08 goil gCDW-1. Finally, a new lipid extraction method using green solvents was developed, which allowed to extract and purify 11.29 g of oils, corresponding to 35% of the cell dry weight. The carbon footprint of this laboratory-scale production was estimated to be 71 - 434 kgCO2eq kg-1 microbial oil, with electricity consumption of the fermentation step as the main factor. Simulation of the process in a 300L fermenter suggests that the electricity consumption, and therefore the overall impact, can be drastically reduced with scale-up. Conclusions The proposed process is promising in terms of production and has the advantage of not being in competition with edible resources and land use. However, the microbial oil yield and the extraction process must be optimized to make the process sustainable.支撑《废弃柠檬皮提取物制备微生物油脂及其碳足迹》研究发现的补充数据与原始基础数据。 摘要 背景 农业领域是农业工业固体有机废弃物的主要产出方之一。此类废弃物多采用焚烧或填埋处置方式，造成潜在资源的大量浪费，而这些资源本可用于生产高价值化学品。本研究针对废弃柠檬提取物（LE），即废弃柠檬皮与果肉加工产生的含水副产物，开发了一套发酵制备微生物油脂的工艺，并对其环境影响进行了评估。微生物油脂应用场景广泛，可用于塑料与橡胶复合材料中的增塑剂，亦可作为化妆品配方中的保湿剂。 方法与结果 对LE的表征结果显示，高压灭菌工艺可有效提升易利用葡萄糖与果糖的浓度，分别达到28.77±0.08 g·L⁻¹与25.68±0.27 g·L⁻¹。同时测定了其氮含量，计算得到碳氮比为85，该比例恰好可诱导所选微生物细胞工厂实现油脂积累。因此，研究人员将产油酵母Cutaneotrichosporon oleaginosum接种于未改性的LE基培养基中，在2L生物反应器中进行培养，最终油脂积累量达0.47±0.08 g·g细胞干重（Cell Dry Weight, CDW）⁻¹。此外，本研究还开发了一种基于绿色溶剂的新型油脂提取方法，成功提取并纯化得到11.29 g油脂，其占细胞干重的比例达35%。 本实验室规模生产工艺的碳足迹估算为71~434 kg二氧化碳当量（carbon dioxide equivalent, CO₂eq）·kg⁻¹微生物油脂，其中发酵阶段的电力消耗为主要影响因子。通过对300L规模发酵罐的工艺模拟可知，扩大生产规模可大幅降低电力消耗，进而显著降低整体环境影响。 结论 本研究提出的工艺在制备与生产维度展现出良好应用前景，且具备不与食用资源及土地使用竞争的优势。不过，当前微生物油脂产率与提取工艺仍需优化，方能实现该工艺的可持续性。