Abstract
Lactic acid (LA) obtained by fermentation of carbohydrates is well-known and widely used in the food sector. This process is as an alternative to the chemical synthesis and ensures several advantages especially in terms of environmental sustainability. In particularly, the opportunity to use agro-food residues as fermentable raw materials could improve the overall process sustainability, without considering the indisputable advantages in terms of waste reduction and residual biomass valorization, in a bio- and circular economy perspective. This research deals with the study and development of the fermentation processes of various waste biomasses from the agro-food industries, including milk whey (MW), ricotta cheese whey (RCW), pear processing residues (PPR), potato pomace (PP), tomato pomace (PT), in order to obtain an experimental protocol applicable to the production of LA. Lactobacillus casei DSM 20011 (ATCC 393), a homofermentative L(+)-LA producing bacterium has been used, starting from small-scale tests to verify of the microorganism to grow in complex medium with different carbon sources and the possible presence of potentially toxic substances for microbial growth. Yields from 27.0 ± 0.3% to 46.0 ± 0.7% have been obtained. Then, a scaling-up was performed in a 1 L batch fermenter, using a mixed medium of RCW and PPR in different ratio. The best LA yield was 78.3% with a volumetric productivity of 1.12 g/L·h in less than 60 h.
Highlights
Agri-food residues refer to organic waste that results from the processing and packaging of animal and/or plant products by the agri-food industry [1]
Biomasses characterization is referred to their effective composition just before being fermented, in order to consider the effect of possible material losses during pretreatments and organic molecules degradation during autoclaving caused by the well-known Maillard reaction
For pear processing residues (PPR), the prompt fermentable fructose represents more than 75% of the Total carbohydrates (TC) [32], whereas tomato pomace (TP) is constituted for about 22% by pectin [38] and potato pomace (PP) of about 75% by starch [5]
Summary
Agri-food residues refer to organic waste that results from the processing and packaging of animal and/or plant products by the agri-food industry [1]. 129 million tonnes per year, with about 25% accounted for the sole postharvest and manufacturing stages [3] Such a large quantity poses the question of high costs of management for collection and transportation, as well as the need of adequate treatment facilities. The separate collection of bio-waste and the enhancement of its valorization rates are still a key issue in EU [5]. This ensure that economically valuable waste materials will be reinjected into the EU economy and prevent detrimental consequences for human health and the environment [6]
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