一株兼具产油和纤维素降解能力的印度血桐 种仁内生菌的筛选及发酵条件优化 Screening and fermentation conditions optimization of endophytes from Macaranga indica seed kernel with both oil production and cellulose degradation capabilities

Abstract

旨在寻找兼具产油和纤维素降解能力的菌株以有效降低发酵成本，进而促进产油微生物的应用。通过苏丹黑B染色法筛选印度血桐种仁中具有产油能力的内生菌，并通过刚果红筛选法初筛、滤纸条崩解实验和产纤维素酶活力测定复筛纤维素降解能力较强的菌株，采用单因素试验对其发酵条件进行优化，并对其产油脂主要脂肪酸组成进行测定。结果表明，印度血桐种仁中共筛选出6株兼具产油能力和纤维素降解的菌株，其中Mi007号菌株的透明圈直径与菌落直径比值（3.16）较大，滤纸崩解情况最佳，产纤维素酶活力（1233 U/mL）最高，其纤维素降解能力最强。优化的发酵条件为酵母粉用量1.0 g/L、pH 6、接种量5.0 mL（40 mL培养基），在此条件下Mi007号菌株有最佳产油量，为409.31 mg/L，所产油脂主要脂肪酸为棕榈酸（C16∶ 0）、硬脂酸（C18∶ 0）和油酸（C18∶ 1）。经测序鉴定，Mi007号菌株为巨大普利斯特氏菌（Priestia megaterium)，序列相似度为99.93%。综上，Mi007号菌株兼具产油和纤维素降解能力，且产油量较高，有望成为克服工业发酵成本问题的备选菌株。In order to identify microorganisms that exhibit both oil production and cellulose degradation capabilities, thereby reducing fermentation costs and promoting the application of oil-producing microorganisms, endophytic microorganisms having oil-producing ability were screened from Macaranga indica seed kernel using Sudan Black-B staining. Subsequently, strains exhibiting strong cellulose degradation ability were initially screened by Congo Red screening method, and rescreened using the filter paper disintegration experiments and cellulase activity measurements, followed by the optimization of fermentation conditions by single factor experiment. The fatty acid composition of the oil produced by the screened strain was determined. The results indicated that six strains capable of simultaneous cellulose degradation and oil production were identified from Macaranga indica seed kernel. Strain Mi007 exhibited the highest ratio of transparent circle diameter to colony diameter (316), demonstrated superior filter paper disintegration, and displayed the highest cellulase activity (12.33 U/mL), indicating its strongest cellulose degradation capability. Strain Mi007 achieved the optimal oil yield of 409.31 mg/L when the yeast dosage was 1.0 g/L, the pH was 6, and the inoculation amount was 5.0 mL(40.0 mL culture medium), C16∶ 0, C18∶ 0 and C18∶ 1 were the main fatty acid of the strain oil. Sequence identification confirmed that strain Mi007 was Priestia megaterium, exhibiting a sequence similarity of 9993%. In summary, Mi007 strain, with both oil production and cellulose degradation capabilities and high oil yield, is expected to be a candidate strain to overcome the cost problem of industrial fermentation.

Keywords

• 植物内生菌；印度血桐种仁；纤维素降解；微生物油脂；发酵条件优化
• plant endophytes; macarange indica seed kernel; cellulose degradation; microbial oil; fermentation condition optimization