Combined polyhydroxyalkanoates (PHA) and 1,3-propanediol production from crude glycerol: Selective conversion of volatile fatty acids into PHA by mixed microbial consortia

Abstract

Crude glycerol is an important by-product of the biodiesel industry, which can be converted into volatile fatty acids (VFA) and/or 1,3-propanediol (1,3-PDO) by fermentation. In this study, a selective conversion of VFA to polyhydroxyalkanoates (PHA) was attained while leaving 1,3-PDO in the supernatant by means of mixed microbial consortia selection strategies. The process showed highly reproducible results in terms of PHA yield, 0.99 ± 0.07 C PHA/C S (0.84 g COD PHA/g COD S), PHA content (76 ± 3.1 g PHA/100 g TSS) and 1,3-PDO recovery (99 ± 2.1%). The combined process had an ultimate yield from crude glycerol of 0.19 g COD PHA and 0.42 g COD 1,3-PDO per g of input COD. The novel enrichment strategy applied for selectively transforming fermentation by-products into a high value product (PHA) demonstrates the significance of the enrichment process for targeting specific bio-transformations and could potentially prove valuable for other biotechnological applications as well.

Effect of hydraulic retention time on the modelling and optimization of joint 1,3 PDO and BuA production from 2G glycerol in a chemostat process

“…(1,3 PDO and PHA) in a two-stage process (see also [50]), with butyric acid being used as a preferred carbon source for the PHA production [52]. The mathematical model predicted that maximum joint production would be reached under the following conditions: pH = 6.4, HRT = 17.6 and 49.3 g/L of glycerol.…”

“…In a previous study the authors have selected different MMC and tested their stability in continuous processes [6,7]. The overall idea was to develop a two-stage process in which glycerol fermentation would be coupled to the production of polyhydroxyalkanoates (PHA) through the selective consumption of butyric acid, while leaving intact the 1,3 PDO, thus facilitating its recovery [50] (or eventually through the conversion of 1,3 PDO and butyric acid to PHA [51]). Therefore, the joint production of 1,3 PDO and butyric acid is of particular interest for the full exploitation of the crude glycerol as a carbon source (in fact butyric acid is considered as a preferred substrate for PHA production [52]), leading to the production of two high-value compounds.…”

A Review on Established and Emerging Fermentation Schemes for Microbial Production of Polyhydroxyalkanoate (PHA) Biopolyesters

“…Using MMC, PHA can be produced at high productivity and low costs due to minor sterility demands, reduced requirements for the equipment and control devices, and, most of all, MMC can utilize inexpensive, complex feedstocks such as carbonaceous domestic or industrial effluents [58,65,67,68]. Auspicious yields and specific productivity were described for MMC processes based on either defined substrates like acetate [64], or inexpensive, complex compounds from wastewater [69], olive oil mill effluents [68], sugar cane molasses [70], food waste [71], crude glycerol phase (CGP) [72], or even toxic phenolics [73]. These complex substrates can either be used directly for PHA production, or they have to be fermented in a first, anaerobic step towards volatile fatty acids (VFAs).…”

Construction of simplified microbial consortia to degrade recalcitrant materials based on enrichment and dilution-to-extinction cultures

“…They are superior compared to single strains with respect to degradative efficiency in many cases (13). Unlike single strains isolation, enrichment process involving directed artificial selection is often used to obtain desired microbial consortia from the environment (14, 15). In general, composition of consortia gradually changes over time, including a richness reduction along with emergence of dominant microbes due to competitive exclusion (16).…”