Effect of wheat bran pre-treatment on isolation of ferulic acid

abstract

English

Ferulic acid (FA) is a highly valued bioactive substance. It has a significant antioxidant effect, antimicrobial, anticancer, antiallergic, hepatoprotective, anti-inflammatory and antiviral effects. Due to these properties, the use of FA in the food, pharmacological and cosmetic industries is extensive. Recently, significant efforts have been made to find nonchemical processes for the preparation of this substance. One possible way to solve this issue is to valorize waste lignocellulosic materials i.e. from the cereal processing industry (Apprich et al., 2014, Stavova et al., 2017). According to FAOSTAT, the world's processing of wheat produces more than 120 million metric tons of wheat bran (WB), which contain a significant amount of FA. However, in the isolation of FA from wheat bran, pretreatment of the raw material is needed. This step is crucial because it helps to remove unwanted components and enhance the efficiency of the isolation process. In this study, the effect of different pretreatments of wheat bran before the process of alkaline hydrolysis for the isolation of FA was tested. The pretreatments that were tested included the removal of protein, starch, and a combination of starch and protein removal. The final pretreatment that was tested involved the removal of starch, lipids, and protein. After the alkaline hydrolysis of native WB, a yield of 1.5 mg/g of FA was obtained. The amount of FA in WB ranges from 1 to 5 mg/g. The effectiveness of alkaline hydrolysis is reported to be between 60% and 90%. Therefore, the yield of 1.5 mg/g FA appears to be realistic and likely the highest possible. However, the content of FA in the obtained hydrolysate was only 0.42%. This result indicates that the hydrolysate contains other components as impurities. After pretreatment of WB with hot water, a yield of 0.99 mg/g of FA was obtained from subsequent alkaline hydrolysis. This indicates that some FA was lost during the hot water pretreatment. However, it was found that the content of FA in the hydrolysate increased to 0.77%. This suggests that some impurities, likely starch, were removed by the hot water wash. The presence of starch in the hot water after the WB pretreatment was confirmed by an iodine test. After pretreatment of WB with 0.05M NaOH, a yield of 1.24 mg/g of FA was obtained from subsequent alkaline hydrolysis. The loss of FA was smaller compared to the pretreatment of WB with hot water. The amount of FA in the hydrolysate was 0.73%. As a result of WB pretreatment with 0.05M NaOH, a significant amount of proteins were removed. By combining both pretreatment processes (firstly washing with hot water followed by 0.05M NaOH extraction) and subsequent alkaline hydrolysis of pretreated WB, a yield of 0.94 mg/g FA was obtained. During the pretreatment process, the loss of FA was registered, similar to the single pretreatments. The amount of FA in the obtained hydrolysate was 0.71%. The results of this work show that the pretreatment of native bran is a desirable step in the isolation of FA from WB. In addition to removing part of the unwanted substances after pretreatment, this step also facilitates alkaline hydrolysis since the pretreatment of the material reduces the viscosity of the solution obtained after hydrolysis and allows better processing of the suspension. However, it was found that part of FA is lost during the pretreatment steps. As part of further study, it is therefore necessary to pay attention to the treatment of liquid fractions obtained during WB pretreatment with the aim of recovering the maximum possible amount of FA before the final process of FA separation from the hydrolyzate, such as utilizing ion exchange techniques.

Ferulic acid, wheat bran, biorefinery, alkaline hydrolysis, pretreatment methods

NÁBĚLEK, J.; DIVIŠ, P.; POŘÍZKA, J.

12. 10. 2023

International Ecological Engineering Society

ZHAW Life Sciences und Facility Management, Güentalstrasse 14, 8820 Wädenswil, Switzerland