Enhanced Anaerobic Mixed Culture Fermentation with Anion-Exchange Resin for Caproate Production

Jiangnan Yu,Chunmei Liu,Wenquan Ruan,Jialin Liao,Zhenxing Huang,Mingxing Zhao,Peng Wu

doi:10.3390/pr7070404

Jiangnan Yu, Chunmei Liu + Show 5 more

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https://doi.org/10.3390/pr7070404

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Abstract

The bioproduction of caproate from organic waste by anaerobic mixed culture is a very attractive technology for upgrading low-grade biomass to a high-value resource. However, the caproate production process is markedly restricted by the feedback inhibition of caproate. In this study, four types of anion-exchange resin were investigated for their enhancing capability in caproate fermentation of anaerobic mixed culture. The strong base anion-exchange resin D201 showed the highest adsorption capacity (62 mg/g), selectivity (7.50), and desorption efficiency (88.2%) for caproate among the test resins. Subsequently, the optimal desorption temperature and NaOH concentration of eluent for D201 were determined. The adsorption and desorption efficiency of D201 remained stable during eight rounds of the adsorption–desorption cycle, indicating a satisfactory reusability of D201. Finally, performances of caproate fermentation with and without resin adsorption for carboxylate were evaluated. The results demonstrated that the final concentration of caproate was improved from 12.43 ± 0.29 g/L (without adsorption) to 17.30 ± 0.13 g/L (with adsorption) and the maximum caproate production rate was improved from 0.60 ± 0.01 g/L/d to 2.03 ± 0.02 g/L/d. In the group with adsorption, the cumulative caproate production was increased to 29.10 ± 0.33 g/L broth, which was 134% higher than that of the control group. Therefore, this study provides effective approaches to enhance caproate production.

Highlights

Caproate is a high-density energy carrier and a high-value added chemical which is applicable in a variety of industries, e.g., petrochemical, pharmaceutical, and food manufacturing [1,2].The production of caproate from waste stream material can simultaneously achieve the recovery of high-value biological products and waste reduction [1,2]
In this study, enhanced caproate production performance was achieved by applying anion-exchange resin to mixed culture-caproate fermentation
The strongly basic anion-exchange resin showed better potential to enhance caproate production and D201 was the optimal resin among the test resins due to its higher adsorption, selectivity, and desorption performance

Summary

Introduction

The production of caproate from waste stream material can simultaneously achieve the recovery of high-value biological products and waste reduction [1,2]. Studies of this technology have recently been intensively reported [3,4,5]. Caproate production is a two-stage fermentation process [6]. The organic waste is hydrolyzed and acidified in the acidification stage to produce short chain carboxylic acids (SCCAs). In the caproate fermentation stage, SCCAs, together with the electron donor, such as ethanol, are utilized by anaerobic mixed culture to biosynthesize caproate [4,5]

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Conclusion