Cai Guiqin, Moghaddam Lalehvash, O'Hara Ian M, Zhang Zhanying
Centre for Tropical Crops and Biocommodities, Queensland University of Technology GPO Box 2432, 2 George St Brisbane QLD 4001 Australia
RSC Adv. 2019 Jan 18;9(5):2539-2550. doi: 10.1039/c8ra08971j.
An integrated microbial oil production process consisting of acidified glycerol pretreatment of sugarcane bagasse, enzymatic hydrolysis, microbial oil production by NRRL 1757 and oil recovery by hydrothermal liquefaction (HTL) of fungal biomass in fermentation broth was assessed in this study. Following pretreatment, the effect of residual pretreatment hydrolysate (containing glycerol) on enzymatic hydrolysis was firstly studied. The residual pretreatment hydrolysate (corresponding to 2.0-7.5% glycerol) improved glucan enzymatic digestibilities by 10-11% compared to the enzymatic hydrolysis in water (no buffer). Although residual pretreatment hydrolysate at 2.0-5.0% glycerol slightly inhibited the consumption of glucose in enzymatic hydrolysate by NRRL 1757, it did not affect microbial oil production due to the consumption of similar amounts of total carbon sources including glycerol. When the cultivation was scaled-up to a 1 L bioreactor, glucose was consumed more rapidly but glycerol assimilation was inhibited. Finally, HTL of fungal biomass in fermentation broth without any catalyst at 340 °C for 60 min efficiently recovered microbial oils from fungal biomass and achieved a bio-oil yield of 78.7% with fatty acids being the dominant oil components (∼89%). HTL also led to the hydrogenation of less saturated fatty acids (C18:2 and C18:3) to more saturated forms (C18:0 and C18:1).
本研究评估了一种综合微生物油脂生产工艺，该工艺包括甘蔗渣的酸化甘油预处理、酶水解、利用NRRL 1757生产微生物油脂以及通过对发酵液中真菌生物质进行水热液化（HTL）来回收油脂。预处理后，首先研究了残余预处理水解液（含甘油）对酶水解的影响。与在水中（无缓冲液）进行酶水解相比，残余预处理水解液（相当于2.0 - 7.5%的甘油）使葡聚糖的酶解率提高了10 - 11%。尽管2.0 - 5.0%甘油的残余预处理水解液略微抑制了NRRL 1757对酶水解产物中葡萄糖的消耗，但由于包括甘油在内的总碳源消耗量相似，因此并未影响微生物油脂的生产。当培养规模扩大到1 L生物反应器时，葡萄糖消耗更快，但甘油同化受到抑制。最后，在340℃无任何催化剂的条件下对发酵液中的真菌生物质进行60分钟的水热液化，可有效地从真菌生物质中回收微生物油脂，生物油产率达到78.7%，脂肪酸是主要的油脂成分（约89%）。水热液化还导致不饱和程度较低的脂肪酸（C18:2和C18:3）氢化为饱和度更高的形式（C18:0和C18:1）。
