Resolving the formidable barrier of oxygen transferring rate (OTR) in ultrahigh-titer bioconversion/biocatalysis by a sealed-oxygen supply biotechnology (SOS)

Xia Hua,Yong Xu,Xin Zhou,Genlai Du

doi:10.1186/s13068-019-1642-1

Xia Hua, Yong Xu + Show 2 more

Open Access

https://doi.org/10.1186/s13068-019-1642-1

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Abstract

BackgroundThe critical issue in the competitiveness between bioengineering and chemical engineering is the products titer and the volume productivity. The most direct and effective approach usually employs high-density biocatalyst, while the weakened mass transfer and evoked foam problem accompany ultrahigh-density biocatalyst loading and substrate/product titer. In high-density obligate aerobic bioconversion, oxygen as electron acceptor is a speed-limiting step in bioprocesses, but sufficient oxygen supply will lead to the foaming which results in a significant reduction in oxygen utilization and the use of additional defoamers. In this study, we designed a novel sealed-oxygen supply (SOS) biotechnology to resolve the formidable barrier of oxygen transferring rate (OTR), for bio-based fuels and chemical production process.ResultsBased on systemic analysis of whole-cell catalysis in Gluconobacter oxydans, a novel sealed-oxygen supply technology was smartly designed and experimentally performed for biocatalytic oxidation of alcohols, sugars and so on. By a simple operation skill of automatic online supply of oxygen in a sealed stirring tank bioreactor of SOS, OTR barrier and foaming problem was resolved with great ease. We finally obtained ultrahigh-titer products of xylonic acid (XA), 3-hydroxypropionic acid (3-HPA), and erythrulose at 588.4 g/L, 69.4 g/L, and 364.7 g/L, respectively. Moreover, the volume productivity of three chemical products was improved by 150–250% compared with normal biotechnology. This SOS technology provides a promising approach to promote bioengineering competitiveness and advantages over chemical engineering.ConclusionSOS technology was demonstrated as an economic and universally applicable approach to bio-based fuels and chemicals production by whole-cell catalysis. The novel technology greatly promotes the competitiveness of bioengineering for chemical engineering, and provides a promising platform for the green and environmental use of biofuels.

Highlights

The critical issue in the competitiveness between bioengineering and chemical engineering is the products titer and the volume productivity
The aerobic microorganisms applied in the industrial bioprocesses require large amounts of molecular oxygen as electron acceptor at the terminus of the cell respiratory electron transfer system [8], and re-oxidized nicotinamide adenine dinucleotide phosphate (NADPH) and/or flavin adenine dinucleotide (FADH) in electron transfer process to release abundant metabolic adenosine triphosphate (ATP) for cell maintenance, growth and catalytic reaction [9]
Design sealed-oxygen supply (SOS) system based on systemic analysis of whole‐cell catalysis of G. oxydans Oxygen is the linchpin dynamics of oxidation reaction in the process of G. oxydans biocatalytic conversion to organic acid

Summary

Introduction

The critical issue in the competitiveness between bioengineering and chemical engineering is the products titer and the volume productivity. The most direct and effective approach usually employs high-density biocatalyst, while the weakened mass transfer and evoked foam problem accompany ultrahigh-density biocatalyst loading and substrate/product titer. We designed a novel sealed-oxygen supply (SOS) biotechnology to resolve the formidable barrier of oxygen transferring rate (OTR), for bio-based fuels and chemical production process. It is well-known that biotechnology and bioengineering techniques possess several advantages over chemical methods, such as moderate reaction conditions, high chemoselectivity, and are environmentally friendly [1]. The most direct and effective approach usually employs high-density biocatalyst [4], while the weakened mass transfer [5] and evoked foam problem inevitably accompany ultrahigh-density biocatalyst loading and substrate/ product titer [6]. Ensuring an oxygen-enriched environment in the broth is a strict requirement for aerobic microorganisms [14]

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