Carota Eleonora, Petruccioli Maurizio, D'Annibale Alessandro, Crognale Silvia
Department for Innovation in Biological, Agro-food and Forest Systems (DIBAF), University of Tuscia, Via S. Camillo De Lellis snc, 01100, Viterbo, Italy.
Heliyon. 2020 Sep 14;6(9):e04801. doi: 10.1016/j.heliyon.2020.e04801. eCollection 2020 Sep.
The aqueous extraction of orange peel waste (OPW), the byproduct of the juice extraction process generated annually in massive amounts (21 Mton), yields a carbohydrate-rich liquid fraction, termed orange peel extract (OPE). Several studies highlight that the combination of glycerol, a biodiesel byproduct, with carbohydrate mixtures might boost microbial lipid production. This study performed first a shaken flask screening of 15 oleaginous yeast strains based on their growth and lipid-producing abilities on OPE- and glycerol-based media. This screening enabled the selection of NRRL 1091 for the assessment of the process transfer in a stirred tank reactor (STR). This assessment relied, in particular, on either single- and double-stage feeding fed-batch (SSF-FB and DSF-FB, respectively) processes where OPE served as the primary medium and nitrogen-containing glycerol-OPE mixtures as the feeding one. The continuous supply mode at low dilution rates (0.02 and 0.01 h for SSF-FB and DSF-FB, respectively) starting from the end of the exponential growth of the initial batch phase enabled the temporal extension of biomass and lipid production. The SSF-FB and DSF-FB processes attained high biomass and lipid volumetric productions (LVP) and ensured significant lipid accumulation on a dry cell basis (Y). The SSF-FB process led to LVP of 20.6 g L after 104 h with volumetric productivity ( ) of 0.20 g L h and Y of 0.80; the DSF-FB process yielded LVP, and Y values equal to 15.92 g L, 0.11 g L h and 0.65, respectively. The fatty acid profiles of lipids from both fed-batch processes were not significantly different and resembled that of oil, a vastly used feedstock for biodiesel production. These results suggest that OPE constitutes an excellent basis for the fed-batch production of lipids, and this process might afford a further option in OPW-based biorefinery.
橙汁提取过程每年会产生大量（2100万吨）的副产品——橙皮废料（OPW），其水相提取物可得到富含碳水化合物的液体部分，称为橙皮提取物（OPE）。多项研究表明，生物柴油副产品甘油与碳水化合物混合物相结合，可能会促进微生物脂质的产生。本研究首先基于15株产油酵母菌株在以OPE和甘油为基础的培养基上的生长和产脂能力，进行了摇瓶筛选。通过该筛选，选择了NRRL 1091用于评估在搅拌罐反应器（STR）中的工艺转移。该评估尤其依赖于单级和双级补料分批发酵（分别为SSF-FB和DSF-FB）工艺，其中OPE作为主要培养基，含氮甘油-OPE混合物作为补料培养基。从初始分批培养阶段的指数生长期结束开始，以低稀释率（SSF-FB和DSF-FB分别为0.02 h和0.01 h）进行连续供应模式，能够延长生物量和脂质生产的时间。SSF-FB和DSF-FB工艺实现了较高的生物量和脂质体积产量（LVP），并确保了基于干细胞重量的显著脂质积累（Y）。SSF-FB工艺在104 h后LVP达到20.6 g/L，体积生产力（ ）为0.20 g/L·h，Y为0.80；DSF-FB工艺产生的LVP、 和Y值分别为15.92 g/L、0.11 g/L·h和0.65。两种分批补料工艺产生的脂质脂肪酸谱没有显著差异，与 油相似， 油是生物柴油生产中广泛使用的原料。这些结果表明，OPE是分批补料生产 脂质的优良基础，该工艺可能为基于OPW的生物炼制提供另一种选择。
