Biocatalysts Laboratory, Deptartment of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, 641 003, India.
Department of Renewable Energy Engineering, Agricultural Engineering College & Research Institute, Tamil Nadu Agricultural University, Coimbatore, 641 003, India.
Microb Cell Fact. 2021 Sep 9;20(1):179. doi: 10.1186/s12934-021-01667-3.
Oleaginous microorganisms are sustainable alternatives for the production of biodiesel. Among them, oleaginous fungi are known for their rapid growth, short life cycles, no light requirement, easy scalability, and the ability to grow in cheap organic resources. Among all the sources used for biodiesel production, industrial wastewater streams have been least explored. We used oleaginous fungi to decontaminate sago processing wastewater and produce biodiesel.
Among the 15 isolates screened for lipid production and starch utilization using the Nile red staining assay and amylase plate screening, three isolates accumulated > 20% (w/w) of their dry cell mass as lipids. The isolate ASEF14 exhibited the highest lipid accumulation (> 40%) and was identified as Aspergillus caespitosus based on the 28S rRNA gene sequencing. The maximum lipid content of 54.4% in synthetic medium (SM) and 37.2% in sago processing wastewater (SWW) was produced by the strain. The Fourier-transform infrared (FTIR) spectroscopy of the fungal oil revealed the presence of functional peaks corresponding to major lipids. Principal component analysis (PCA) of the FTIR data revealed major changes in the fatty acid composition during the transition from the growth phase (Days 1-3) to the lipid accumulation phase (Days 4-7). The fatty acid methyl esters (FAME) analysis of fungal oil from SWW contained 43.82% and 9.62% of saturated and monounsaturated fatty acids, respectively. The composition and percentage of individual FAME derived from SWW were different from SM, indicating the effect of nutrient and fermentation time. The fuel attributes of the SM- and SWW-grown fungal biodiesel (kinematic viscosity, iodine value, cetane number, cloud and pour point, linolenic acid content, FA > 4 double bonds) met international (ASTM D6751, EN 14214) and national (IS 15607) biodiesel standards. In addition to biodiesel production, the strain removed various contaminants such as total solids (TS), total suspended solids (TSS), total dissolved solids (TDS), dissolved oxygen (DO), chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), and cyanide up to 58.6%, 53.0%, 35.2%, 94.5%, 89.3%, 91.3%, 74.0%, 47.0%, and 53.84%, respectively, from SWW.
These findings suggested that A. caespitosus ASEF14 is a potential candidate with high lipid accumulating ability (37.27%), capable of using SWW as the primary growth medium. The medium and incubation time alter the FAME profile of this fungus. The physical properties of fungal oil were in accordance with the biodiesel standards. Moreover, it decontaminated SWW by reducing several polluting nutrients and toxicants. The fungal biodiesel produced by this cost-effective method could serve as an alternate path to meet global energy demand.
产油微生物是生产生物柴油的可持续替代品。其中，产油真菌以其快速生长、生命周期短、无需光照、易于规模化和能够利用廉价有机资源生长而著称。在用于生产生物柴油的所有来源中，工业废水的开发最少。我们使用产油真菌来净化西米加工废水并生产生物柴油。
在用尼罗红染色法和淀粉酶平板筛选法筛选用于脂质生产和淀粉利用的 15 个分离株后，有 3 个分离株的细胞干重积累超过 20%（w/w）为脂质。分离株 ASEF14 表现出最高的脂质积累（>40%），并根据 28S rRNA 基因测序鉴定为粗糙脉孢菌。在合成培养基（SM）和西米加工废水（SWW）中，该菌株的最大脂质含量分别为 54.4%和 37.2%。真菌油的傅里叶变换红外（FTIR）光谱显示存在与主要脂质相对应的功能峰。FTIR 数据的主成分分析（PCA）表明，在从生长阶段（第 1-3 天）到脂质积累阶段（第 4-7 天）的过渡过程中，脂肪酸组成发生了重大变化。来自 SWW 的真菌油的脂肪酸甲酯（FAME）分析含有 43.82%和 9.62%的饱和脂肪酸和单不饱和脂肪酸，分别。来自 SWW 的 FAME 的组成和百分比与 SM 不同，表明了营养物质和发酵时间的影响。SM 和 SWW 生长的真菌生物柴油的燃料特性（运动粘度、碘值、十六烷值、浊点和倾点、亚油酸含量、FA>4 个双键）符合国际（ASTM D6751、EN 14214）和国家标准（IS 15607）生物柴油标准。除了生产生物柴油外，该菌株还去除了各种污染物，例如总固体（TS）、总悬浮固体（TSS）、总溶解固体（TDS）、溶解氧（DO）、化学需氧量（COD）、生物需氧量（BOD）、总氮（TN）、总磷（TP）和氰化物，分别达到 58.6%、53.0%、35.2%、94.5%、89.3%、91.3%、74.0%、47.0%和 53.84%，来自 SWW。
这些发现表明，粗糙脉孢菌 ASEF14 是一种具有高脂质积累能力（37.27%）的潜在候选物，能够将 SWW 用作主要生长培养基。培养基和培养时间改变了这种真菌的 FAME 图谱。真菌油的物理性质符合生物柴油标准。此外，它通过减少几种污染营养物质和有毒物质来净化 SWW。通过这种具有成本效益的方法生产的真菌生物柴油可以作为满足全球能源需求的替代途径。
