Microbial polyhydroxyalkanoate synthesis from field pea starch hydrolysate

Significant growth is anticipated in the plant-based protein industry over the next five years. To ensure sector viability into the future, development of value-added applications for starchy by-products from pulse crops such as field peas is essential. This study demonstrates utilization of field pea starch — more crystalline than other starches — as an inexpensive carbon source for microbial poly(3-hydroxyalkanoate) (PHA) biopolymer production. Commercial enzymes typically used for cereal starches (Stargen and a cocktail of Stargen, Optimash, GC626) generated sugar hydrolysates with similar glucose content (~80 g L −1 ) from 10 % (w v −1 ) crude pea starch. When used as a carbon source for PHA biosynthesis in several strains, the Stargen hydrolysate supported comparable PHA synthesis characteristics as commercial glucose, with the strains Paraburkholderia sacchari and Burkholderia thailandensis performing best. During cultivation on 15 g L −1 glucose-equivalent concentration of the Stargen hydrolysate, the intracellular PHA content reached up to 48 % of the dry biomass and the PHA titer was around 2 g L −1 in shake flasks. Despite having higher protein content, the triple-enzyme hydrolysate yielded no obvious benefit compared to the Stargen treatment for growth or PHA synthesis. The results suggest that Stargen alone can effectively hydrolyze crude field pea starch, and the resulting hydrolysate is suitable for production of PHA biopolymers. To our knowledge, this is the first study producing PHA from field pea starch hydrolysates in submerged cultivation, highlighting a promising co-product strategy to support a sustainable and resilient plant protein sector. • Field pea starch is a low-cost by-product of the pulse protein processing. • Enzymes for cereal starch effectively hydrolyzed crystalline pea starch. • Polyhydroxyalkanoates (PHAs) were produced from the glucose-rich hydrolysates. • P. sacchari and B. thailandensis achieved PHA titers of ~2 g L −1 in shake flasks. • PHA production can add value to pulse crop processing by-products.