Poly(β-hydroxybutyric acid) thermoplastic production by Alcaligenes latus: Behavior of fed-batch cultures

Abstract

Fed-batch culture of Alcaligenes latus, ATCC 29713, was investigated for producing the intracellular bioplastic poly(b±hydroxybutyric acid), PHB. Constant rate feeding, exponentially increasing feeding rate, and pH-stat fed batch methods were evaluated. pH-stat fed batch culture reduced or delayed accumulation of the substrate in the broth and led to signi®cantly enhanced PHB productivity relative to the other modes of feeding. Presence of excessive substrate appeared to inhibit PHB synthesis, but not the production of cells. In fed-batch culture, the maximum speci®c growth rate (0.265 h )1 ) greatly exceeded the value (0.075 h )1 ) previously observed in batch culture of the same strain. Similarly, the maximum PHB production rate (up to 1.15 g á l )1 á h )1 ) was nearly 8-fold greater than values observed in batch operations. Fed-batch operation was clearly superior to batch fermentation for producing PHB. A low growth rate was not a prerequisite for PHB accumulation, but a reduced or delayed accumulation of substrate appeared to enhance PHB accumulation. Under the best conditions, PHB constituted up to 63% of dry cell mass after 12 h of culture. The average biomass yield coef®cient on sucrose was about 0.35, or a little less than in batch fermentations. The highest PHB concentrations attained were about 18 g á l )1 . List of Symbolsconcentration of ammonium ion (mg á l )1 ) C C mass fraction of sucrose in the feed ()) C N mass fraction of ammonia in pH control solution ()) C T mass fraction of trace elements in feed solution ()) E element F C mass¯ow rate of the sucrose solution (g á h )1 ) F N mass¯ow rate of the ammonia solution (g á h )1 ) F s feed mass¯ow rate (g á h )1 ) F T mass¯ow rate of the trace element solution (g á h )1 ) m maintenance coef®cient ()) N concentration of nitrogen source (g á l )1 ) PHA polyhydroxyalkanoate PHB poly(b-hydroxybutyric acid) q S maximum speci®c sucrose consumption rate (g á l )1 á h )1 ) q P speci®c product formation rate (g á l )1 á h )1 ) q P max maximum speci®c product formation rate (g á l )1 á h )1 ) S total amount of substrate in fermenter at time t (g) SDS sodium dodecyl sulfate S 0 mass fraction of the substrate in feed ()) t time (h) t 0x-intercept in Eq.(1) (h) TES trace element solution or its amount in the medium (ml á l )1 ) X 0 total initial biomass in fermenter (g) X t total biomass in fermenter at time t (g) Y P/S product yield coef®cient on sucrose ()) Y P/X speci®c product yield coef®cient ()) Y R/N PHB-free biomass yield coef®cient on nitrogen source ()) Y R/S PHB-free biomass yield coef®cient on carbon source ()) Y R/T PHB-free biomass yield coef®cient on trace elements ()) Y X/S biomass yield coef®cient on sucrose ())Greek symbols d mass fraction of PHB in cells ()) l speci®ed growth rate (h )1 ) l max maximum speci®c growth rate (h )1 )

Biosynthesis and characterization of copolymer poly(3HB-co-3HV) from saponified Jatropha curcas oil by Pseudomonas oleovorans

“…These were of particular importance, since they identiWed the PHA as a copolymer consisting of Table 1) [16,39]. 13 C NMR identiWed the J. curcas PHA as a mixed polymer and supports the data from ESI-TOF MS, which indicate the presence of the valerate unit. The peak at 1.32 ppm was not identiWed but was also present in the 13 C NMR spectrum of the commercial homopolymer P(3HB).…”

“…A suspension containing 80 mg sample/ 2.0 mL chloroform-d (CDCl 3 ) was vortexed for 30 min, Wltered (0.22-m Wlter), and 1.0 mL placed into 5-mm NMR tubes. The following parameters were selected for analysis of samples: temperature, 30°C; sweep width, 20.69 ppm; 64 K data points; 30° excitation pulse; acquisition delay, 6 s. 13 C NMR data were ascertained with similar parameters and new samples. Acquisition time was set for 2 h/sample.…”

“…PHAs consist of about 120 diVerent (R)-3-hydroxyacid (3HA) monomeric units with the most common being poly( -hydroxybutyrate)(PHB) [19] and poly( -hydroxyvalerate) (PHV) [5]. Several bacteria use various carbon substrates to produce PHAs under limiting growth conditions [1,13,24,[26][27][28]50]. Pseudomonas oleovorans, for example, employs substrates requiring -oxidation, but not those requiring fatty acid de novo synthesis to produce medium chain length (mcl) PHAs [11,12,14,17,23,36,43,49,51].…”

Improved productivity of poly (3-hydroxybutyrate) (PHB) in thermophilic Chelatococcus daeguensis TAD1 using glycerol as the growth substrate in a fed-batch culture

“…To date, Alcaligenes latus (Yamane et al 1996;Grothe and Chisti 2000), Methylobacterium sp. GW2 (Yezza et al 2006) and Zobellella denitrificans strain MW1 (Ibrahim and Steinbüchel 2010b) and C. daeguensis TAD1 Yang et al 2012;Xu et al 2014) have been used as model organisms for growth-associated PHB accumulation, and the behaviors of these strains with glucose in fed-batch culture have been studied in detail.…”

Enhancing the Production of Polyhydroxyalkanoate Biopolymer by Azohydromonas Australica Using a Simple Empty and Fill Bioreactor Cultivation Strategy

“…One of the major objectives during fermentation process optimization is to enhance the product yield and productivity while minimizing the substrate limitation and inhibition problem during the cultivation. Fed-batch fermentation strategy has been used by various researchers with an aim to maximize polyhydroxybutyrate PHB concentration and avoid substrate inhibitions and/or limitations at the same time [11][12][13][14] . However, the success of such fed-batch strategy(ies) requires development of an on-line monitoring and control system for estimation of residual substrates and/or fresh nutrients addition.…”