Evaluation of Fed-Batch Fermentation for Production of Polyhydroxybutyrate With a Banana Pulp Juice Substrate From an Agro Industrial By-Product

Mónica Arias-Roblero,Vanny Mora-Villalobos,Carmela Velazquez-Carrillo

doi:10.3389/fsufs.2021.681596

Mónica Arias-Roblero, Vanny Mora-Villalobos + Show 1 more

Open Access

https://doi.org/10.3389/fsufs.2021.681596

Copy DOI

Abstract

Pollution resulting from the persistence of plastics in the environment has driven the development of substitutes for these materials through fermentation processes using agro-industrial wastes. Polyhydroxybutyrate (PHB) is a rapidly biodegradable material with chemical and mechanical properties comparable to those of some petroleum-derived plastics. PHB accumulates intracellularly as an energy reserve in a wide variety of microorganisms exposed to nutritionally imbalanced media. The objective of this study was to evaluate the use of a banana waste product as a carbon source for PHB production. PHB was extracted by acid methanolysis and detected by gas chromatography-mass spectrometry. Eleven bacterial strains with potential for PHB production were evaluated by in vitro fermentation in a culture broth containing fructose as the carbon source and limited nitrogen. A 22 central composite rotational design was applied to optimize the concentrations of banana juice and ammonium chloride needed to maximize the PHB-producing biomass concentration. The process was then carried out in a 3 L fed-batch fermentation system that included an initial stage of biomass growth. Banana juice was used as the carbon source and fructose pulses were added to maintain the test sugar concentrations of 30, 40, and 50 g/L. The control strain, Cupriavidus necator (ATCC 17699), produced 2.816 g/L of PHB, while productivity of the most promising isolate, C. necator (CR-12), was 0.495 g/L. Maximum biomass production was obtained using 5% banana juice and 2 g/L ammonium chloride. PHB production was not detected in fed-batch fermentations supplemented with 30 or 40 g/L of fructose, while the mean PHB production in fermentations with 50 g/L of fructose was 1.3 g/L.

Highlights

Biotechnological alternatives to conventional plastics are increasingly important in industry worldwide (Sirohi et al, 2020) as they promote sustainability in the agriculture industry and strengthen rural economies (Li and Wilkins, 2021)
PHB production in native strains was not quantifiable (Measured PHB concentrations stood between detection and quantification limits defined for the method), except for CR-12 which showed a concentration of 0.5 g PHB/L culture broth
The enzymatic maceration pretreatment applied to the banana pulp allowed the conversion of the substrate into simple sugars molecules, primarily glucose (Velásquez-Arredondo et al, 2010) and fructose, as well as an increment on proteins and polysaccharides accessibility (Naranjo et al, 2014; Tsang et al, 2019), and facilitated the development of fermentation processes for PHB production

Summary

Introduction

Biotechnological alternatives to conventional plastics are increasingly important in industry worldwide (Sirohi et al, 2020) as they promote sustainability in the agriculture industry and strengthen rural economies (Li and Wilkins, 2021). Polyhydroxybutyrate (PHB), the most common biodegradable homopolymer of polyhydroxyalcanoates (PHA) (Maity et al, 2020), has numerous applications in food, agriculture, medicine and other industries (Li et al, 2017; Sirohi et al, 2020). It naturally accumulates intracellulary in a large number of microorganisms (Oliveira et al, 2004; Mohapatra et al, 2020; Mostafa et al, 2020; Pati et al, 2020; Penkhrue et al, 2020; Nygaard et al, 2021). Some bacteria synthesize PHB as part of the primary metabolism; others, such as Cupriavidus necator, require a nutritional imbalance in the culture media to activate the synthesis metabolism (Grousseau et al, 2014; Getachew and Woldesenbet, 2016; Amini et al, 2020)

Objectives

Methods

Results

Conclusion