3-hydroxypropionic acid production from Brewer's spent grain with an engineered Issatchenkia orientalis

Area of Science:

• Biotechnology
• Biochemical Engineering
• Industrial Microbiology

Background:

• 3-Hydroxypropionic acid (3-HP) is a key platform chemical with diverse industrial applications.
• Brewer's spent grain (BSG) is an abundant, low-cost lignocellulosic byproduct from brewing, representing a sustainable feedstock.
• Efficient conversion of BSG into valuable chemicals like 3-HP requires optimized pretreatment and fermentation strategies.

Purpose of the Study:

• To develop a proof-of-concept for producing 3-HP from BSG using a one-pot CaO pretreatment and an engineered acid-tolerant yeast strain.
• To investigate the impact of various factors, including acid type, nitrogen source, NaHCO3 addition, and BSG deproteinization, on 3-HP production.
• To establish a robust fermentation process for value-added chemical production from biomass without external nitrogen supplementation.

Main Methods:

• A novel one-pot CaO pretreatment method was employed for BSG hydrolysis.
• An engineered, acid-tolerant Issatchenkia orientalis IoDY01H strain was used for 3-HP fermentation.
• Optimization experiments evaluated different acid types (H2SO4, H3PO4) for pH adjustment, nitrogen sources (yeast extract-peptone vs. synthetic complete medium), NaHCO3 supplementation, and BSG deproteinization.

Main Results:

• Yeast extract-peptone medium enhanced 3-HP titers by 13.3% compared to synthetic complete medium using pure sugars.
• NaHCO3 supplementation increased 3-HP titers to 7.8 g/L in YPDX medium.
• H2SO4 for pH adjustment in BSG hydrolysates yielded higher 3-HP (7.4 g/L) than H3PO4 (6.8 g/L).
• Deproteinization of BSG significantly improved xylose recovery and resulted in the highest 3-HP titer of 8.7 g/L without nitrogen supplementation.

Conclusions:

• The study successfully demonstrated the production of 3-HP from BSG using a combined one-pot pretreatment and fermentation approach.
• Optimizing pretreatment conditions, particularly deproteinization, and fermentation parameters like pH adjustment and NaHCO3 addition are crucial for maximizing 3-HP yield.
• The developed process offers a sustainable route for valorizing BSG into valuable chemicals, highlighting the potential for nitrogen-free fermentation.