From Agri-Food Wastes to Polyhydroxyalkanoates through a Sustainable Process

Abstract

The biologically-derived polymers polyhydroxyalkanoates (PHAs) are biodegradable and can be considered a valuable alternative to conventional fossil-based plastics. However, upstream and downstream processes for PHA production are characterized by high energy and chemical consumption and are not economically competitive with petroleum-based polymers. Aiming to improve both the environmental and economical sustainability of PHAs production, in this work, corn straw was used as raw material to obtain a mixture of fermentable sugars after microwave-assisted flash hydrolysis (2 min, 0.01 g/L, 50.7% yield). A mixed microbial culture enriched from dairy industry waste was used for fermentation in a shake flask, allowing us to achieve good poly(hydroxy-butyrate-co-hydroxy-valerate) yields (41.4%, after 72 h of fermentation). A scale-up in a stirred tank bioreactor (3 L) gave higher yields (76.3%, after 96 h), allowing in both cases to achieve a concentration of 0.42 g/L in the fermentation medium. The possibility of producing PHAs from agricultural waste using a mixed microbial culture from the food industry with enabling technologies could make the production of biopolymers more competitive.

Polyhydroxyalkanoates (PHAs) from Endophytic Bacterial Strains as Potential Biocontrol Agents against Postharvest Diseases of Apples

“…The rich composition of the soapstock makes it possible to fully realize the biosynthetic potential of the studied bacterial strains. Similar to our results, previous studies showed effective production of PHAs on media containing different agro-industrial wastes [14,[21][22][23]. It is known that substrates entail major costs in PHA production [2,19].…”

Harnessing Agri-Food Waste as a Source of Biopolymers for Agriculture

“…Campanari et al [101] (Table 6, Entry 1) utilized a multi-stage process in which they selected PHA-storing microorganisms under feast and famine (FF) conditions in a sequencing batch reactor (SBR) and found out that the PHA production is widely influenced by the selection of PHA producers, which is in turn influenced by the organic loading rate (ORL). Verdini et al (Table 6, Entry 2) [102] used corn straw saccharified with the aid of microwave technology and obtained a greater yield during scaling up in a stirred tank 3L bioreactor, compared to a shake flask. Moreover, the authors were also able to determine the specific PHA that was being produced, which was poly(3-hydroxybutyrateco-3-hydroxyvalerate) (PHBV).…”

Advances in the Food Packaging Production from Agri-Food Waste and By-Products: Market Trends for a Sustainable Development

“…The agri-food waste and by-products can be used by microorganisms as feedstock for fermentation in the production of biopolymers [81]. Polyhydroxyalkanoates (PHA) and polylactides (polylactic acid) (PLA), in particular, are the most studied polymers to date and are widely used due to their numerous applications [82]. Figure 2 presents a general PHA/PLA production flowchart that follows the sustainable concepts of a closed loop and clean production.…”