Zeleke Birhanu, Muleta Diriba, Dinka Hunduma, Tsegaye Dereje, Hassen Jemal
Department of Applied Biology, School of Applied Natural Science, Adama Science and Technology University, Adama, Oromia, Ethiopia.
Environmental Biotechnology Unit, Institute of Biotechnology, Addis Ababa University, Addis Ababa, Ethiopia.
PLoS One. 2025 Jun 23;20(6):e0312922. doi: 10.1371/journal.pone.0312922. eCollection 2025.
There is a high demand for microbial pigments as a promising alternative for synthetic pigments, primarily for safety and economic reasons. This study aimed at the optimization of yellowish-orange pigment production by Exiguobacterium aurantiacum using agro-waste extracts as a growth substrate. Air samples were collected using the depositional method. Pure cultures of pigment producing bacteria were isolated by subsequent culturing on fresh nutrient agar medium. The potent isolate was identified using MALDI-TOF technique. Screening of culture conditions was done via Plackett-Burman design that highlighted culture agitation rate, initial medium pH, and yeast extract concentration as the most significant variables (p < 0.0001) in influencing pigment production with further optimization step using response surface methodology. Among the tested agro-waste decoctions, tomato waste extract was selected for fermentation due to higher optical density of the isolate when cultivated in it compared to the other agro-waste extracts. Under optimized conditions, 0.96 g/L of pigment was extracted from 4.73 g/L of culture biomass, representing a 1.6-fold increase compared to un-optimized conditions. Spectroscopic and chromatographic analyses confirmed the presence of various functional groups, with carotenoids identified as the primary compounds responsible for the yellowish-orange pigmentation. These findings demonstrate the feasibility of enhancing bacterial pigment production using agro-waste substrates, highlighting its potential for large-scale industrial applications.
由于安全和经济方面的原因，微生物色素作为合成色素的一种有前景的替代品，其需求量很大。本研究旨在利用农业废弃物提取物作为生长底物，优化橙色黄杆菌产生橙黄色色素的条件。采用沉积法采集空气样本。通过在新鲜营养琼脂培养基上继代培养，分离出产生色素的细菌纯培养物。使用基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）技术鉴定优势菌株。通过Plackett-Burman设计对培养条件进行筛选，该设计突出了培养搅拌速率、初始培养基pH值和酵母提取物浓度是影响色素产生的最显著变量（p < 0.0001），并使用响应面法进行进一步优化。在测试的农业废弃物煎剂中，选择番茄废弃物提取物进行发酵，因为与其他农业废弃物提取物相比，该菌株在其中培养时具有更高的光密度。在优化条件下，从4.73 g/L的培养生物量中提取了0.96 g/L的色素，与未优化条件相比增加了1.6倍。光谱和色谱分析证实存在各种官能团，类胡萝卜素被确定为导致橙黄色色素沉着的主要化合物。这些发现证明了使用农业废弃物底物提高细菌色素产量的可行性，突出了其在大规模工业应用中的潜力。
