Junyong Zhu

High Titer Ethanol and Lignosulfonate Production from SPORL Pretreated Poplar at Pilot Scale

Poplar NE222 (Populus deltoides Bartr. ex Marsh × P. nigra L.) wood chips were pretreated in a 390 L pilot-scale rotating wood-pulping digester using a dilute sulfite solution of approximately pH  1.8 at 160°C for 40 min for bioconversion to ethanol and lignosulfonate (LS). An estimated combined hydrolysis factor (CHF) of 3.3 was used to scale the pretreatment temperature and time from laboratory bench scale experiments, which balanced sugar yield and inhibitor formation to facilitate high titer ethanol production through fermentation using S. cerevisiae YRH400 without detoxification. A terminal ethanol titer of 43.6 g L-1 with a yield of 247 L tonne wood-1 was achieved at total solids loading of 20%. The relatively low ethanol yield compared with yield from SPORL-pretreated softwoods was due to inefficient utilization of xylose. The LS from SPORL has a substantially higher phenolic group (Ph-OH) content although it is less sulfonated and has a lower molecular weight than a purified commercial softwood LS, and therefore has potential for certain commercial markets and future novel applications through further processing.

Integrated production of furfural and levulinic acid from corncob in a one-pot batch reaction incorporating distillation using step temperature profiling

Furfural and levulinic acid (LA) are potential major renewable platform chemicals for producing biochemicals and biofuels. In this study, integrated conversion of corncob to furfural and LA was carried out in a one-pot system using p-toluenesulfonic acid (p-TsOH) and step temperature profiling. A batch reaction incorporating distillation (BRD) resulted in a good furfural production yield of 61.6% based on the corncob xylan content for the hydrolysis conditions tested. Distillation not only reduced furfural loss due to side reactions to humins, but also resulted in a fairly pure and concentrated furfural solution. At the end of the first distillation step, the reaction temperature was increased to convert hexoses into LA with a maximal production yield of 61.3 ± 7.8% based on corncob glucan content. LA was extracted with good yield as LA–ester using low-cost alcohols and then phase separated to recycle alcohols and p-TsOH. Good recyclability and reusability of p-TsOH and alcohols were demonstrated.