Impact of Hydrolysis Methods on the Utilization of Agricultural Residues as Nutrient Source for D-lactic Acid Production by <i>Sporolactobacillus inulinus</i>

• Main Authors: Silvia Brock, Anja Kuenz, Ulf Prüße
• Format: Article
• Language: English
• Published: MDPI AG 2019-01-01
• Series: Fermentation
• Subjects: <i>Sporolactobacillus inulinus</i>; <span style="font-variant: small-caps">d</span>-lactic acid; nutrient sources; agricultural residues; chemical hydrolysis; enzymatic hydrolysis
• Online Access: https://www.mdpi.com/2311-5637/5/1/12

<span style="font-variant: small-caps;">d</span>-lactic acid is a building block for heat resistant polylactic acid, a biobased polymer with a high potential. Nevertheless, an economically efficient industrial process for <span style="font-variant: small-caps;">d</span>-lactic acid production still needs to be implemented. Yeast extract is an expensive nutrient source, which is used to fulfill the complex nutritional requirements in lactic acid fermentations. The substitution of yeast extract by cheap alternative nutrient sources is a challenge in many fermentation processes. In this study, chemical and enzymatic hydrolysis techniques for protein rich agricultural residues and their effectiveness are compared, as well as their impact on the <span style="font-variant: small-caps;">d</span>-lactic acid production of <i>Sporolactobacillus inulinus</i>. An efficient substitution of yeast extract could be achieved by a variety of agricultural residues, hydrolysed with 3M H₂SO₄, demonstrating the much higher versatility and effectiveness of this method compared to enzymatic methods. In a fed-batch experiment with chemically hydrolyzed rapeseed meal and minimal supplementation, a lactic acid titer of 221 g L^&#8722;1 and an overall productivity of 1.55 g (L h)^&#8722;1 (96% yield) were obtained.