Tailor-made pretreatments facilitate the downstream processes and techno-economic of the lignocellulose-to-lipid routes: A review

Lignocellulose-derived microbial lipid has attracted widespread attention as promising feedstock in biodiesel and oleochemicals industries. However, the techno-economics of the lignocellulose-to-lipid routes have been severely hampered by the biomass recalcitrance which impeding the degradation of lignocellulose into fermentable sugars. A variety of pretreatment technologies have been developed for significantly enhancing the enzyme digestibility, essential for the deconstruction of biomass. However, the complicated influences of pretreatment on the downstream processes have rarely been comprehensively evaluated and designed. Some pretreatments routinely exert adverse effects on the downstream processes, especially the enzymatic hydrolysis and lipid fermentation processes. It is essential to maximize the positive effects and avoid the negative effects of pretreatments on the subsequent processes. It is very meaningful to select and design tailor-made pretreatment strategies to facilitate the downstream steps. In this review, the compatibility of lignocellulosic biomass pretreatment and lipid overproduction was discussed systematically. The major general- and tailor-made indicators to evaluate pretreatment methods in lignocellulose-to-lipid route were illustrated and discussed. A requirement-oriented concept for selection and design of tailor-made pretreatment strategies to facilitate the downstream steps including enzymatic hydrolysis and lipid production were emphasized. A variety of tailor-made pretreatments beneficial for the downstream processes were proposed for achieving cost-effective lipid production. This review provides important guidelines and references for the researchers in selecting and developing tailor-made pretreatment strategies, thereby to facilitate the commercial success of lignocellulose-to-lipid technology.