About

C. Yiwei Zhang is an Assistant Professor of Consumer Science at the University of Wisconsin-Madison. His research lies at the intersection of economics and psychology, focusing on understanding how consumers make financial decisions and how these decisions impact well-being and market outcomes. Additionally, his work explores how the financial decisions of households may be unintentionally influenced by features of the institutional environment surrounding them. Prior to joining UW-Madison, Zhang was a Postdoctoral Research Fellow at the University of Chicago, Booth School of Business, and he also worked as an Economist in the Office of Research at the Consumer Financial Protection Bureau. He holds a B.S. in Economics and a B.S. in Mathematics from the Massachusetts Institute of Technology and earned his Ph.D. from the University of Pennsylvania, Wharton School's program in Applied Economics.

Research topics

• Chemistry
• Engineering
• Waste management
• Biology
• Pulp and paper industry
• Environmental science
• Organic chemistry
• Biochemistry

Selected publications

• An evolved strain of Spathaspora passalidarum produces ethanol from sugarcane bagasse and switchgrass lignocellulosic hydrolysates

  SSRN Electronic Journal · 2026-01-01

  preprintOpen access
  PublisherDOI

• Switchgrass Steroidal Saponins Reduce Fungal Disease but Decrease Yeast Fermentation Yield

  GCB Bioenergy · 2025-12-04

  articleOpen access

  ABSTRACT Increasing the production of bioproducts from lignocellulosic feedstocks requires improvement in both field production and biorefinery efficiency. When plant traits arise that improve field production but decrease biofuel yield, these trade‐offs can represent challenges in the entire production process. To examine trade‐offs between field and production traits, we examined factors underlying switchgrass resistance to fungal rust pathogens in field conditions and factors that impede yeast fermentation in the lab using repeated measurements on a switchgrass genetic diversity panel. We found that the same switchgrass genotypes that showed high fungal pathogen resistance also showed recalcitrance to yeast fermentation. These switchgrass genotypes were mostly from the Atlantic genetic group, which had high levels of specialized metabolites of the saponin class. Among 1589 metabolites identified through metabolomics, we found that saponins were among the most likely to explain variation in both rust infection and fermentation yield using random forest feature selection, and that only four of these were sufficient to explain 57.9% of the variation in rust susceptibility. Through follow‐up testing in recalcitrant biomass, we found that the bacterium Zymomonas mobilis does not suffer the same inhibition as the yeast Saccharomyces cerevisiae , and that the addition of ergosterol (thought to be the fungal cellular target of saponin inhibition) rescues yeast fermentation. Several lines of evidence point to a central role for saponins as key metabolites protecting switchgrass from fungal pathogens and interfering with yeast fermentation, underscoring an ongoing need for collaboration between plant breeders and biofuel production scientists.

  PublisherDOI

• pH adjustment increases biofuel production from inhibitory switchgrass hydrolysates

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-01-12 · 2 citations

  preprintOpen access

  Abstract Biofuels derived from renewable and sustainable lignocellulosic biomass, such as switchgrass, offer a promising means to limit greenhouse gas emissions. However, switchgrass grown under drought conditions contains high levels of chemical compounds that inhibit microbial conversion to biofuels. Fermentation of drought switchgrass hydrolysates by engineered Saccharomyces cerevisiae and Zymomonas mobilis generates less ethanol than fermentation of hydrolyzed switchgrass from an average rainfall year. Here, we demonstrate that this inhibitory effect can be alleviated by altering the pH of drought-switchgrass hydrolysates made from two different pretreatment methods: Ammonia Fiber Expansion (AFEX) and Soaking in Aqueous Ammonia (SAA). Fermentation rates and biofuel production from AFEX- and SAA-pretreated switchgrass hydrolysates from normal and drought years were higher at pH 5.8 than at pH 5.0 for both S accharomyces cerevisiae and Zymomonas mobilis . Additionally, SAA pretreatment of drought switchgrass enabled increased fermentation rates and titers compared to AFEX pretreatment. Using a synthetic mimic of switchgrass hydrolysate, we identified relief from pH-dependent inhibition by lignocellulose-derived inhibitors as the cause of increased biofuel production above a pH of 5.0. These results demonstrate that SAA pretreatment and pH adjustment can significantly improve fermentation and biofuel production from switchgrass hydrolysates and especially from drought-switchgrass hydrolysates by industrial microorganisms.

  PublisherOA PDFDOI

• Developmentally specific physiological and metabolic responses support drought resilience in switchgrass and constrain biofuel yield

  Journal of Experimental Botany · 2025-12-08

  articleOpen access

  Switchgrass (Panicum virgatum) is a promising bioenergy crop due in part to its resilience to drought stress. However, the significance of drought timing remains poorly understood, both from a plant biology perspective and in terms of its impact on downstream biofuel production. This study determines the developmental stage-specific physiological and metabolic responses of switchgrass to drought stress and their implications for biofuel production using a custom-built programmable irrigation system. Vegetative-, flowering-, and senescence-stage drought significantly reduced carbon dioxide assimilation and stomatal conductance without affecting biomass yield. Metabolic profiling revealed significant accumulation of glucose, fructose, quinic acid, shikimate, and γ-aminobutyric acid (GABA) during vegetative-stage drought, while flowering and senescence stages exhibited limited metabolic changes. Similarly, specialized metabolites also displayed distinct developmental patterns, with vegetative-stage drought driving the most pronounced metabolic alterations. Thermochemically treated and hydrolyzed switchgrass biomass from vegetative-stage drought showed elevated lignocellulose-derived compounds and saponins, with the latter most positively correlating with fermentation lag times. Conversely, senescence-stage drought enhanced ethanol yields while lowering saponin levels in the hydrolysates. While vegetative-stage drought enhanced physiological resilience, it compromises downstream biofuel production by introducing fermentation inhibitors, particularly saponins.

  PublisherDOI

• A prospective and comparative study on improving the diagnostic accuracy of early gastric cancer based on deep convolutional neural network real-time diagnosis system (with video)

  Surgical Endoscopy · 2025-01-22 · 6 citations

  article
  PublisherDOI

• Evaluating the industrial potential of emerging biomass pretreatment technologies in bioethanol production and lipid recovery from transgenic sugarcane

  Sustainable Energy & Fuels · 2025-01-01 · 2 citations

  articleOpen access

  The selection of pretreatment methods is critical to achieving high product yields during bioconversion of lignocellulosic biomass.

  PublisherOA PDFDOI

• An evolved strain of <i>Spathaspora passalidarum</i> produces ethanol from sugarcane bagasse and switchgrass lignocellulosic hydrolysates

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-09-28

  preprintOpen access

  Abstract Lignocellulosic hydrolysates, derived from plant biomass, contain various inhibitors that can hinder microbial growth. This study aimed to enable the growth and ethanol production by the xylose-fermenting yeast Spathaspora passalidarum in the presence of lignocellulosic hydrolysate inhibitors, particularly acetic acid. Ultraviolet (UV)-induced mutagenesis and adaptive laboratory evolution (ALE) were used to select for mutants with higher tolerance to these inhibitors. The initial mutant strain, MT01, was selected for increased growth in medium containing xylose and acetic acid. This strain underwent further evolution, resulting in the strain ME3.5.5, which showed significant improvements in both growth and ethanol production compared to the parental strain when tested in sugarcane bagasse hemicellulosic hydrolysate (SBHH). Genomic analysis identified non-synonymous and frameshift mutations in four genes, including CYR1 (encoding adenylate cyclase). These findings suggest that genetically optimized S. passalidarum strains could play a crucial role in advancing industrial bioethanol production from lignocellulosic biomass by overcoming the inhibitory effects of compounds found in lignocellulosic hydrolysates.

  PublisherOA PDFDOI

• Developmentally-specific physiological and metabolic responses support drought resilience in switchgrass and constrains biofuel yield

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-06-01

  preprintOpen access

  Abstract Switchgrass ( Panicum virgatum ) is a promising bioenergy crop due in part to its resilience to drought stress. However, the significance of drought timing remains poorly understood, both from a plant biology perspective and its impact on downstream biofuel production. This study determines the developmental stage-specific physiological and metabolic responses of switchgrass to drought stress and its implications for biofuel production using a custom-built programmable irrigation system. Vegetative, flowering, and senescence-stage drought significantly reduced CO 2 assimilation, and stomatal conductance without affecting biomass yield. Metabolic profiling revealed significant accumulation of glucose, fructose, quinic acid, shikimate and GABA during vegetative-stage drought, while flowering and senescence stages exhibited limited metabolic changes. Similarly, specialized metabolites also displayed distinct developmental patterns, with vegetative-stage drought driving the most pronounced metabolic alterations. Thermochemically-treated and hydrolyzed switchgrass biomass from vegetative-stage drought showed elevated lignocellulose-derived compounds and saponins with the latter most positively correlating with fermentation lag times. Conversely, senescence-stage drought enhanced ethanol yields while lowering saponin levels in the hydrolysates. While vegetative-stage drought enhanced physiological resilience, it compromises downstream biofuel production by introducing fermentation inhibitors, particularly saponins.

  PublisherOA PDFDOI

• pH adjustment increases biofuel production from inhibitory switchgrass hydrolysates

  Bioresource Technology · 2025-05-09 · 6 citations

  articleOpen access
  PublisherOA PDFDOI

• Research and experiments of a new premedication for improving mucosal visibility during esophagogastroduodenoscopy

  BMC Gastroenterology · 2025-07-01

  articleOpen access

  BACKGROUND: Mucus and bubbles are important factors that can reduce endoscope visibility. This may result in missed diagnoses of minor or early lesions. Therefore, dimethicone, such as drugs used before esophagogastroduodenoscopy (EGD), is called premedication. There is no uniform premedication worldwide. Moreover, the clinical effects of existing preoperative medications cannot meet the needs of endoscopists. AIMS: The purpose of our study was to screen effective food additive components that can be used before EGD. In addition, we conducted in vitro and in vivo comparative experiments to evaluate the effectiveness of the compounds. METHODS: An in vitro foaming model was established to evaluate the function of food additives. Through preliminary experiments, we determined the lowest effective dose, ratio and application method of each main component. Two different levels of in vitro comparison experiments were designed. Egg white and water were mixed as foaming agents in the in vitro foaming model, whereas gastric juice was used in the in vitro gastric juice experiment. In vivo experiments were performed in a live rabbit model. We divided the samples into three groups: food additive 1 (papain) and food additive 2,3 (sucrose polyoxypropylene, polypropylene glycol) (group A), pronase and dimethicone (group B), and water alone (group C). In vitro experiments, the protein concentration difference and visibility difference suggest the ability of mucolytic agents, and the residual bubble amount and the minimum amount of defoamer required to suppress bubbles are the outcome measures for defoaming agents. The mucosal visibility score (MVS) is the outcome measure in experiments with live animals. RESULTS: Three food additives were selected. Papain is a proteolytic enzyme, whereas sucrose polyoxypropylene and polypropylene glycol are defoamers. The lowest effective dose of papain was 500 mg. The optimal ratio of the two defoamers was 7:3, and the minimum effective doses were 116.7 mg and 50 mg, respectively. In the foaming model, the median protein concentrations differences of the three groups were 21.89 mg/mL, 21.54 mg/mL and 0.16 mg/mL. The visibility difference was 9.7 mL for group A and 4.1 mL for group B. The residual bubble amount of group A (0 mL) was significantly lower than those of group B (312.5 mL) and C (487.5 mL). The average minimum dose of defoamer used was 5.1 mL in group A. In group B, the foam could not be completely suppressed in four experiments, and in group C, ten experiments failed. In the gastric juice experiment, the median protein concentration differences between the two groups were 18.62 mg/mL and 17.33 mg/mL (P > 0.05). The visibility differences between the two groups were 5.65 and 4.00 mL (P = 0.017). Both groups A and B could completely eliminate the foam after the addition of 0.5 mL of different reagents. The minimum amount of defoamer needed to suppress bubbles in group A was slightly lower than that in group B (0.65 mL vs. 1.60 mL), but the difference was still not statistically significant (P = 0.155). In vivo experiments, the new premedication in group A could remove the mucus and foam completely compared with group B.The mean MVS decline rate of group A was significantly higher than that of group B (73.53% Vs. 39.39%, P < 0.05). CONCLUSION: Proteolytic enzyme (papain) and two food defoamers (sucrose polyoxypropylene and polypropylene glycol) had superior effects on pronase and dimethicone. It may become a more effective preoperative medication regimen, but further research is needed.

  PublisherOA PDFDOI

Frequent coauthors

• Joshua J. Coon

  Morgridge Institute for Research

  88 shared

• Trey K. Sato

  Great Lakes Bioenergy Research Center

  79 shared

• Robert Landick

  University of Wisconsin–Madison

  76 shared

• Jose Serate

  Great Lakes Bioenergy Research Center

  59 shared

• Dan Xie

  Central China Normal University

  52 shared

• Alan Higbee

  Energy Center of Wisconsin

  51 shared

• Edward L. Pohlmann

  Great Lakes Bioenergy Research Center

  50 shared

• Mick McGee

  Great Lakes Bioenergy Research Center

  40 shared