Abstract
This work examines the potential of the predatory bacterium Bdellovibrio bacteriovorus HD100, an obligate predator of other Gram-negative bacteria, as an external cell-lytic agent for recovering valuable intracellular bio-products produced by prey cultures. The bio-product targets to be recovered were polyhydroxyalkanoates (PHAs) produced naturally by Pseudomonas putida and Cupriavidus necator, or by recombinant Escherichia coli strains. B. bacteriovorus with a mutated PHA depolymerase gene to prevent the unwanted breakdown of the bio-product allowed the recovery of up to 80% of that accumulated by the prey bacteria, even at high biomass concentrations. This innovative downstream process highlights how B. bacteriovorus can be used as a novel, biological lytic agent for the inexpensive, industrial scale recovery of intracellular products from different Gram-negative prey cultures.
Highlights
Properties of reduced crystallinity, elasticity, hydrophobicity, low oxygen permeability and biodegradability
The B. bacteriovorus Bd3709/P. putida KT2440 co-culture showed PHA content similar to that of the control culture (P. putida without B. bacteriovorus) after 24 h of incubation [0.85 g l−1 (80% of the initial PHA produced by the P. putida KT2440 cells)] (Table 1)
The obligate predator B. bacteriovorus has long been proposed as an alternative for antibiotics, given its ability to attack Gram-negative bacteria[2,8,9,10,11,12]
Summary
Properties of reduced crystallinity, elasticity, hydrophobicity, low oxygen permeability and biodegradability. Unconventional mcl-PHAs bearing bespoke functional moieties in their side chains can be produced using different biotechnological strategies[18,19] Their condition as intracellular bio-products makes their recovery difficult and expensive[20,21]. Several attempts have been carried out to mimic such procedures by using phage lysis genes to disrupt recombinant cells accumulating PHA22–26 These systems are species-specific and require engineering of the production chassis[26], which limit the broad range applicability of this methodology. It has been suggested that this hydrolysis is the result of an extracellular-like mcl-PHA depolymerase (PhaZBd), which forms part of B. bacteriovorus’s hydrolytic arsenal[27,28,29] The potential of this predator as a downstream tool for intracellular bio-product recovery is shown in the present work by engineering B. bacteriovorus HD100 to avoid it degrading the prey-produced PHA. The results provide proof-of-principle that this system could be used in the production of PHA and other intracellular bio-products
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