Use of apple pomace, glycerine, and potato wastewater for the production of propionic acid and vitamin B12

Abstract

Propionic acid bacteria (PAB) are a source of valuable metabolites, including propionic acid and vitamin B12. Propionic acid, a food preservative, is synthesized from petroleum refining by-products, giving rise to ecological concerns. Due to changing food trends, the demand for vitamin B12 has been expected to increase in the future. Therefore, it is necessary to look for new, alternative methods of obtaining these compounds. This study was conducted with an aim of optimizing the production of PAB metabolites using only residues (apple pomace, waste glycerine, and potato wastewater), without any enzymatic or chemical pretreatment and enrichment. Media consisting of one, two, or three industrial side-streams were used for the production of PAB metabolites. The highest production of propionic acid was observed in the medium containing all three residues (8.15 g/L, yield: 0.48 g/g). In the same medium, the highest production of acetic acid was found — 2.31 g/L (0.13 g/g). The presence of waste glycerine in the media had a positive effect on the efficiency of propionic acid production and P/A ratio. The concentration of vitamin B12 obtained in the wet biomass of Propionibacterium freudenreichii DSM 20271 ranged from 90 to 290 µg/100 g. The highest production of cobalamin was achieved in potato wastewater and apple pomace, which may be a source of the precursors of vitamin B12 — cobalt and riboflavin. The results obtained show both propionic acid and vitamin B12 can be produced in a more sustainable manner through the fermentation of residues which are often not properly managed. Key points • The tested strain has been showed metabolic activity in the analyzed industrial side-streams (apple pomace, waste glycerine, potato wastewater). • All the side-streams were relevant for the production of propinic acid. • The addition of waste glycerine increases the propionic acid production efficiency and P/A ratio. • B12 was produced the most in the media containing potato wastewater and apple pomace as dominant ingredients.

Reprocessing of side-streams towards obtaining valuable bacterial metabolites

“…In Poland (the largest producer of apples in the European Union), the production of pomace is in the range of 400–600 thousand tons/year. Apple pomace contains sugars (glucose, fructose), B vitamins and micro- and macro-elements (Magyar et al 2016 ; Piwowarek et al 2022 ). Their composition suggests that they can serve as a culture medium.…”

“…This solution enriched the soil with nitrogen compounds assimilated by plants, and it was also cheap and easy to implement. However, when there is prolonged irrigation with potato wastewater, the soil becomes clogged and loses water permeability, and this method also leads to water eutrophication (Piwowarek et al 2022 ). Ciecholewska-Juśko et al ( 2021 ) used potato wastewater to cultivate K. xylinus bacteria (28 °C, 7 days).…”

“…The popularisation of biodiesel is hampered by high production costs, which are largely due to the necessity to utilise the side-streams generated. Therefore, much cheaper methods of glycerine biodegradation are needed (Piwowarek et al 2022 ). Soemphol et al ( 2018 ) used crude glycerol (from biodiesel production) as a carbon source (30 °C, 14 days) for Gluconaceter xylinus BNKC19 which was mixed with the HS broth — achieving a yield of 12.31 g BC/L.…”

“…The advantage of PAB is also their rich enzyme system, which allows them to use many different carbon sources. In addition, literature data show that they are able to grow in media containing by-products of technological processes, which creates the prospect of obtaining metabolites of these microorganisms with the simultaneous disposal of industrial side-streams (Feng et al 2011 ; Yang et al 2018 ; Castro et al 2021 ; Piwowarek et al 2022 ). Another advantage of these microorganisms is the fact that some PAB have GRAS and QPS status, thanks to which both living cells of these microorganisms and their metabolites can be used in food production, which is important in the context of PA or another PAB metabolite (e.g.…”

“…hot water extraction (necessary to extract nutrients from tchem — e.g. sweet lime pulp, pineapple peel, apple pomace) (Cavka et al 2013 ; Wang and Yang 2013 ; Soemphol et al 2018 ; Dubey et al 2018 ; Wang et al 2020 ; Castro et al 2021 ; Piwowarek et al 2022 ). It seems, however, that the benefits of pre-treatment far outweigh the disadvantages of such action, which are mainly related to financial outlays and lengthening the process.…”