Fermentation of Air Currents Assisted Particle Separation (ACAPS) by-product streams from barley for bioethanol production

• Author / Creator

  Lu, Yeye

•       To offset biofuel production costs, a biorefining approach was employed that enables the co-production of high-value products. Barley starch concentrate is a by-product generated during isolation of  β-Glucan from barley grains via the Air Currents Assisted Particle Separation (ACAPS) technology. This study was aimed at establishing a fermentation approach for bioethanol production from a low-value by-product stream. It is anticipated that this study will (1) minimize low-cost by-products from the β-Glucan isolation process; (2) alleviate economic stress on bioethanol production from conventional grains; and (3) increase the economic return from the  ACAPS process.  
  

  The isolation of β-Glucan from Fibar barley using ACAPS technology generates a starch concentrate that is efficiently converted to ethanol (86.7 ± 3.5%) following the established
  fermentation protocol in our lab. Furthermore, enzymatic hydrolysis of barley starch concentrate mash is significantly more efficient compared to conventional wheat mash, producing more than 2-fold greater amount of glucose after only 2 h. Then, the timing of addition as well as the requirement of FERMGENTM 2.5X for hydrolysis of barley starch concentrate mash were studied.
  It was found that barley starch concentrate does not require FERMGENTM 2.5X for hydrolysis. Thus, the effect of omitting other enzymes during hydrolysis of barley starch concentrate mash was studied. It was observed that complete hydrolysis of barley starch concentrate mash can be achieved with STARGENTM 002 only, and there was no specific advantage of adding FERMGENTM 2.5X, OPTIMASHTM TBG and GC 626. Moreover, particle size distribution of wheat flour, barley flour and barley starch concentrate indicated that barley starch concentrate has a larger surface area per unit volume, which likely contributes to the higher accessibility to STARGENTM 002.

  The next step was to obtain hydrolysis kinetics for barley starch concentrate mash that were similar to the wheat benchmark by decreasing the STARGENTM 002 concentration. In this starch hydrolysis study, it was observed that when FERMGENTM 2.5X, OPTIMASHTM TBG and GC 626 were omitted, hydrolysis of barley starch concentrate mash with 0.5X dosage of STARGENTM 002 showed similar enzymatic kinetics to the wheat benchmark using all four enzymes. Therefore, the impact of lower STARGENTM 002 dosage and adding supplements on ethanol production was examined. The lower STARGENTM 002 dosage may help generate lower sugar levels for reduced osmotic stress, thereby potentially improving ethanol yields with less enzyme cost. Here, results show that fermentations incorporating barley starch concentrate and 0.25X dosage of STARGENTM 002 (with no FERMGENTM, OPTIMASHTM TBG and GC 626) displayed similar ethanol yield efficiency as the wheat benchmark, however, phosphorus supplementation was required.
  
  To summarize, the barley starch concentrate examined in this study is a promising feedstock for bioethanol production compared to the wheat benchmarks commonly used in industry. This study successfully optimized the simultaneous saccharification and fermentation (SSF) while controlling rates of hydrolysis and avoiding osmotic stress on yeasts. Considerable cost saving is possible during production of bioethanol from barley starch concentrate by using decreasing
  dosages of STARGENTM 002, and omitting the other enzymes typically used in wheat fermentations. This fermentation approach not only ferments barley starch concentrate efficiently but also likely creates a protein enriched distiller grains that could be valuable as animal feed. It is possible that protein would be concentrated dramatically in barley starch concentrate and higher than the protein in barley DDGS, due to the removal of fiber from ACAPS process. The development of ACAPS by-product-based biorefinery would involve effective bioconversion of barley starch concentrate for the production of two high-value compounds, bioethanol and the coproduct (DDGS), which will make the entire process more sustainable and economically feasible.

• Subjects / Keywords

  • Bioethanol
  • Fermentation
  • Air Currents Assisted Particle Separation
  • Barley

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-f6my-7672

• License

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