Enhanced butanol and single-cell oil production from triticale straw via sequential ABE-oleaginous fermentation with interstitial VFA sharing

This study investigates a sequential process using triticale straw (TSW) as a substrate, integrating acetonebutanol-ethanol (ABE) fermentation with in-situ butanol extraction, followed by oleaginous fermentation of the residual medium containing volatile fatty acids (VFAs) to produce single-cell oil (SCO). Using XAD-4 Amberlite adsorbent for in-situ ABE separation, the residual broth was converted to SCO by Cryptococcus aureus. Pretreatment of the straw with either dilute acid (1 % H2SO4) or alkaline (1 % NaOH) was followed by enzymatic hydrolysis using Cellic (R) CTec2 enzymes, achieving a glucose yield of 85 % at the optimal condition (170 degrees C, 1 %NaOH). The untreated TSW showed a total sugar concentration of 4.12 g/L after 72 h, with production of 0.68 g/L butanol, 0.17 g/L ethanol, and 0.70 g/L SCO in the subsequent fermentation stage. Pretreatment significantly enhanced ABE production, with dilute acid pretreatment generating 28.0 g/L of total sugars and resulting in 9.0 g/L of solvents in the subsequent ABE fermentation. The highest ABE production (11.82 g/L) was obtained from the alkali-pretreated straw at 170 degrees C. XAD-4 Amberlite further increased ABE concentration to 12.97 g/L. Optimal biomass and lipid production (9.96 g/L and 3.25 g/L, respectively) were also attained following alkaline pretreatment. These results demonstrate the potential of triticale straw for sustainable butanol and lipid production.