Enhancing the bioconversion of ferulic acid from alkaline hydrolysate of corn cobs to vanillin by Amycolatopsis thermoflava under nutrient limitation and reducing sugar control

Abstract

BACKGROUND The use of commercially available ferulic acid (FA) as a precursor for vanillin production is costly. The utilization of agro‐waste as a starting material provides an alternative to obtain FA at a low cost and establish an economically profitable production system. In this work, optimization of ultrasound‐assisted extraction conditions for releasing FA from corn cobs using alkaline treatment was conducted. Further, bioconversion of FA from the crude hydrolysate of corn cobs to vanillin using Amycolatopsis thermoflava was performed. RESULTS Since autoclaved hydrolysate was unfavorable for cell growth and vanillin formation, pasteurization was proposed. However, the presence of contaminants limited the entire process. Aiming to suppress the growth of contaminants and increase vanillin yield, novel strategies of limiting and controlling the nutrients for the strain were developed. Optimal hydrolysis conditions (NaOH concentration = 0.5 M, solid loading = 10% for 30 min) produced hydrolysate with relatively high titers of FA (715 mg L−1) and p‐coumaric acid (1025 mg L−1). To improve vanillin production from FA, four parameters (including the effects of sterilization method, nutrient limitation, initial biomass concentration, and reducing sugar control) were investigated. By adopting these strategies and performing bioconversion of FA to vanillin with an initial biomass concentration of 1.5 g L−1, the yield of vanillin was significantly increased by 29.5‐fold to 477.4 mg g−1, compared to bioconversion using autoclaved hydrolysate. CONCLUSION This approach represents a relatively economical method for vanillin production from agro‐waste because it uses crude hydrolysate, requires minimum nutrients, and involves non‐modified organisms with a relatively short bioconversion time (17 h). © 2022 Society of Chemical Industry (SCI).

Biotransformation of maize bran‐derived ferulic acid to vanillin using an adapted strain of Amycolatopsis sp. ATCC 39116

“…However, the yield of ferulic acid and vanillin was very low that is, 0.46 mg vanillin/g ferulic acid. In another study, alkaline hydrolysate of corn cob was used to produce 0.28 g/L of vanillin per g/L of ferulic acid 25 . This vanillin titer is slightly higher than the titer in the current study; however, the extracted ferulic acid yield is much lower.…”

“…In another study, alkaline hydrolysate of corn cob was used to produce 0.28 g/L of vanillin per g/L of ferulic acid. 25 This vanillin titer is slightly higher than the titer in the current study; however, the extracted ferulic acid yield is much lower. Torres et al 21 have also reported vanillin production from the alkaline hydrolysate of corn cob using genetically engineered Escherichia coli JM109/pBB1.…”

“…Encouragingly, ~10%–15% increase was observed in the vanillin yield from standard ferulic acid as well as isolated ferulic acid stream when 0.4 g/L of vanillic acid was added. This value is higher than the earlier similar studies performed by Luziatelli et al and Nirwana et al 10,25 The experimental mean values of vanillin yield in the presence and absence of vanillic acid for both standard, as well as isolated ferulic acid, were compared by Student's t ‐test to be statistically significant ( p < 0.05). The difference in the assimilation rate between standard and maize bran isolated ferulic acid and the presence of certain impurities in the stream may account for the variation in vanillin yield in instances.…”

“…Ferulic acid was determined to be 2.3 g ± 0.06/100 g (DW) of maize bran using an extraction process developed in‐house. Maximum ferulic acid yields obtained so far using methanolic alkaline extraction were 0.61/100 g of pineapple peels and 0.71/100 g corn cob, respectively 25,26 . However, the purity of the current crude ferulic acid extract from maize bran was ~5% (w/w) due to the presence of other impurities such as polymeric and oligomeric lignin, lignans, proteins, polysaccharides, ash, and salts 20 .…”

“…Maximum ferulic acid yields obtained so far using methanolic alkaline extraction were 0.61/100 g of pineapple peels and 0.71/100 g corn cob, respectively. 25,26 However, the purity of the current crude ferulic acid extract from maize bran was $5% (w/w) due to the presence of other impurities such as polymeric and oligomeric lignin, lignans, proteins, polysaccharides, ash, and salts. 20 The presence of lignin and other impurities negatively affected the bioconversion process, hindering the process altogether.…”