Mingjie Jin

Publications (19) View all

• Article: Low Temperature and Long Residence Time AFEX Pretreatment of Corn Stover

  Bryan D. Bals, Farzaneh Teymouri, Tim Campbell, Mingjie Jin, Bruce E. Dale
  [show abstract] [hide abstract]
  ABSTRACT: Low temperature and long residence time pretreatments have been proposed as an alternative to conventional pretreatments within a centralized biorefinery, allowing for a decentralized pretreatment without high energy costs. Ammonia fiber expansion (AFEX™) pretreatment may be uniquely suitable for decentralized pretreatment, and this study considers the possibility of decreasing the temperature in AFEX pretreatment of corn stover. AFEX pretreatment at 40°C and 8h produced comparable sugar and ethanol yields as conventional AFEX pretreatment at high temperatures and short residence time during subsequent hydrolysis and fermentation. Increasing the ammonia loading at these temperatures tends to increase digestibility, although the moisture content of the reaction has little effect. This study suggests a greater flexibility in AFEX pretreatment conditions than previously thought, allowing for an alternative approach for decentralized facilities if the economic conditions are appropriate. KeywordsAFEX–Biofuel–Corn stover–Pretreatment–Ammonia–Regional processing
  BioEnergy Research 05/2012; 5(2):372-379. · 3.56 Impact Factor
• Article: Metabolic flux analysis on arachidonic acid fermentation

  Mingjie Jin, He Huang, Kun Zhang, Jie Yan, Zhen Gao
  [show abstract] [hide abstract]
  ABSTRACT: The analysis of flux distributions in metabolic networks has become an important approach for understanding the fermentation characteristics of the process. A model of metabolic flux analysis of arachidonic acid (AA) synthesis in Mortierella alpina ME-1 was established and carbon flux distributions were estimated in different fermentation phases with different concentrations of N-source. During the exponential, decelerating and stationary phase, carbon fluxes to AA were 3.28%, 8.80% and 6.97%, respectively, with sufficient N-source broth based on the flux of glucose uptake, and those were increased to 3.95%, 19.21% and 39.29%, respectively, by regulating the shifts of carbon fluxes via fermentation with limited N-source broth and adding 0.05% NaNO3 at 96 h. Eventually AA yield was increased from 1.3 to 3.5 g·L−1. These results suggest a way to improve AA fermentation, that is, fermentation with limited N-source broth and adding low concentration N-source during the stationary phase.
  Frontiers of Chemical Engineering in China 04/2012; 1(4):421-426.
• Source

  Available from: Ming W Lau

  Article: An integrated paradigm for cellulosic biorefineries: utilization of lignocellulosic biomass as self-sufficient feedstocks for fuel, food precursors and saccharolytic enzyme production

  Ming W Lau, Bryan D Bals, Shishir P S Chundawat, Mingjie Jin, Christa Gunawan, Venkatesh Balan, A Daniel Jones, Bruce E Dale
  [show abstract] [hide abstract]
  ABSTRACT: Simultaneously achieving economic, environmental and social sustainability is a major challenge for the emerging renewable fuel industry. We approach this problem by demonstrating a cellulosic biorefinery paradigm which produces ethanol and food precursors using lignocellulosic biomass as the exclusive source for carbohydrates and minerals. Enzymatic hydrolysate from Ammonia Fiber Expansion (AFEX)-pretreated corn stover at 18% w/w solids loading was found to be nutrient-rich. This hydrolysate was fermented completely within 48 h in two stages to produce ethanol and native yeast cells. An in-house saccharolytic enzyme production using AFEX-pretreated corn stover as carbohydrate source greatly reduces the dependence on commercial enzymes. The inducer mixture is 2.5–7 times more potent than lactose, a common enzyme inducer. Economic analysis indicates that the proposed paradigm is substantially more cost-effective relative to the 2005 NREL model. This improvement is largely attributed to the native yeast cells co-production and the reduction of enzyme cost through the in-house production. Despite great promise, cellulosic biofuels such as ethanol are struggling to be commercially realized due to high processing costs and low profit margins. Decreasing the costs of low-margin commodities such as fuels requires driving down input costs or increasing revenue by generating valuable co-products. In this paper, we take a holistic approach to lignocellulosic biomass utilization to achieve cost reductions by both routes. The well-known approach to biofuel production via the biochemical route uses as much carbohydrate as possible for ethanol production, the remaining biomass for heat and power generation, and relies on expensive, external sources for hydrolytic enzymes and downstream fermentation nutrients. In contrast, by using Ammonia Fiber Expansion (AFEXÔ) pretreatment, we are able to preserve all nutrients necessary for fermentation, with available excess nutrients used to produce yeast for nutraceuticals, food, and feed related applications (hence, partly offsetting the ''food vs. fuel'' issue of growing dedicated bioenergy crops). In addition, in this novel approach to producing cellulosic biofuels, a small fraction of the pretreated biomass carbohydrates is used to induce and express hydrolytic enzymes at a significantly lower cost. When combined with yeast recycling for improved xylose fermentation, we estimate that these process improvements can decrease the cost of ethanol production by $$0.50 per gallon. The creation of a new multibillion dollar renewable liquid fuel industry demands extensive financial investments, novel technology developments, nationwide policy changes and innovative thinking. The technologies described here are representative of the approaches that can be used to develop this industry. By obtaining additional value via utilization of the entire cellulosic feedstock rather than only the carbohydrate fractions, these and other upcoming process improvements will be necessary to establish a commercially viable bio-based alternative to crude oil derived fuels and chemicals.
  Energy & Environmental Science 03/2012; 5:7100-7110. · 9.61 Impact Factor
• Article: Complex physiology and compound stress responses during fermentation of alkali-pretreated corn stover hydrolysate by an Escherichia coli ethanologen.

  Michael S Schwalbach, David H Keating, Mary Tremaine, Wesley D Marner, Yaoping Zhang, William Bothfeld, Alan Higbee, Jeffrey A Grass, Cameron Cotten, Jennifer L Reed, Leonardo da Costa Sousa, Mingjie Jin, Venkatesh Balan, James Ellinger, Bruce Dale, Patricia J Kiley, Robert Landick
  [show abstract] [hide abstract]
  ABSTRACT: The physiology of ethanologenic Escherichia coli grown anaerobically in alkali-pretreated plant hydrolysates is complex and not well studied. To gain insight into how E. coli responds to such hydrolysates, we studied an E. coli K-12 ethanologen fermenting a hydrolysate prepared from corn stover pretreated by ammonia fiber expansion. Despite the high sugar content (∼6% glucose, 3% xylose) and relatively low toxicity of this hydrolysate, E. coli ceased growth long before glucose was depleted. Nevertheless, the cells remained metabolically active and continued conversion of glucose to ethanol until all glucose was consumed. Gene expression profiling revealed complex and changing patterns of metabolic physiology and cellular stress responses during an exponential growth phase, a transition phase, and the glycolytically active stationary phase. During the exponential and transition phases, high cell maintenance and stress response costs were mitigated, in part, by free amino acids available in the hydrolysate. However, after the majority of amino acids were depleted, the cells entered stationary phase, and ATP derived from glucose fermentation was consumed entirely by the demands of cell maintenance in the hydrolysate. Comparative gene expression profiling and metabolic modeling of the ethanologen suggested that the high energetic cost of mitigating osmotic, lignotoxin, and ethanol stress collectively limits growth, sugar utilization rates, and ethanol yields in alkali-pretreated lignocellulosic hydrolysates.
  Applied and environmental microbiology 03/2012; 78(9):3442-57. · 3.69 Impact Factor
• Article: Consolidated bioprocessing (CBP) of AFEX™-pretreated corn stover for ethanol production using Clostridium phytofermentans at a high solids loading.

  Mingjie Jin, Christa Gunawan, Venkatesh Balan, Bruce E Dale
  [show abstract] [hide abstract]
  ABSTRACT: Consolidated bioprocessing (CBP) using Clostridium phytofermentans (ATCC 700394) on ammonia fiber expansion (AFEX™)-treated corn stover (AFEX™-CS) at a low solids loading showed promising results [Jin et al. (2011) Biotechnol Bioeng 108(6): 1290-1297]. However, industrial relevant process requires high solids loading. Therefore, we studied high solids loading CBP performance on AFEX™-CS. The factors potentially affecting the performance including solids loading, CBP products acetate and ethanol, and degradation products resulting from pretreatment were investigated. At 4% (w/w) glucan loading, C. phytofermentans performed well on AFEX™-CS with no nutrients supplementation and reached similar sugar conversions as a fermentation with nutrients supplementation. A glucan conversion of 48.9% and a xylan conversion of 77.9% were achieved after 264 h with 7.0 g/L ethanol and 8.8 g/L acetate produced. Relatively high concentrations of acetate produced at high solids loading was found to be the major factor limiting the CBP performance. Degradation products in AFEX™-CS helped enhance ethanol production.
  Biotechnology and Bioengineering 02/2012; 109(8):1929-36. · 3.95 Impact Factor