From Waste-to-Wealth Catalysis Lab Discovery to Process Design
Bio-oil derived from biomass pyrolysis can serve as fuel when blended with diesel or as a feedstock to produce value-added products. Catalytic cracking using the HZSM-5 zeolite catalyst presents a promising method to convert bio-oils into valuable hydrocarbons, addressing their high oxygen content and instability. Utilizing a self-designed fluid catalytic cracking (FCC) unit and HZSM-5, we initially investigated the catalytic cracking reaction pathways and catalyst deactivation mechanisms of model compounds with various functional groups found in bio-oil. Our findings indicate that this process primarily yields C6–C8 aromatics and C2–C4 olefins (Selectivity: ethylene > propylene > butylene), along with C1–C5 alkanes and COₓ gases. We proposed a catalyst deactivation mechanism wherein coke formation, originating from long-chain aliphatic/aromatic precursors, evolves into catalytic coke that blocks pores and rapidly reduces activity. Subsequently, we evaluated the co-catalytic cracking of raw bio-oil with waste cooking oil using HZSM-5. This co-cracking process enhances the yield of olefins and aromatics, suppresses coke formation, and significantly reduces oxygen content by utilizing waste cooking oil as a hydrogen donor to stabilize oxygenates. This integrated approach not only upgrades problematic bio-oil into refinery-compatible feedstocks but also offers a cost-effective method for recycling waste cooking oils, demonstrating considerable potential for sustainable fuel and chemical manufacturing from diverse waste streams.
Building directly on our foundational laboratory research, a patented integrated unit was developed, encompassing thermal cracking, stratification, catalytic hydrogenation, catalytic cracking, and separation units. This innovation translates core laboratory discoveries into a scalable industrial process, securing novel methods and apparatuses for transforming waste biomass into valuable chemicals.
Combating Stress-induced Bacterial Persistence
Environmental nutrient variations prompt the persister formation, contributing to biofilm, recurrent infections, and the evolution of genetic resistance. Specifically, shifting nutrients to fatty acids induces persister formation in E. coli, with the accumulation rate of the fatty acid degradation enzyme FadD determining the duration of the transient tolerance period. A nutrient shift from glycerol to oleic acid results in low persistence against ampicillin due to a reactive oxygen species (ROS)-mediated killing mechanism. Conversely, a shift from glucose to oleic acid results in high persistence against multiple antibiotics. This phenotype is mediated by (p)ppGpp, which initiates a feedback loop that inhibits phospholipid and fatty acid synthesis, thereby allowing evasion of antibiotic killing. Based on these findings, strategies to combat persister formation have been proposed, offering promising avenues for targeted therapeutic interventions that could enhance antibiotic effectiveness and improve stability and efficiency in bioproduction processes.
Genetic Circuit Design for Robust Bioproduction
ROS accumulation during microbial fermentation negatively affects bioproduction and causes mutations, which further impede bioproduction. To address this, a ROS fluorescent biosensor was developed to evaluate the effects of oxidative stress on bioproduction. Additionally, a synthetic genetic circuit was designed to prevent stress-induced low producers from dominating the population during fermentation, thereby improving production titer.