Exploring the fermentation characteristics of acetic and lactic acid bacteria for the development of novel sugar-based beverages

Raner, Blaž (author), Čadež, Neža (mentor), O Sullivan, Tadhg (comentor)

Fermented products are well known for their nutritional and health benefits. Recently, there has been an increasing interest for novel fermented beverages by the consumers. This presents an opportunity for the food industry to explore alternative substrates and microorganisms for the production of novel fermented drinks. In our research we focused on gaining a deeper understanding of the fermentation characteristics of two selected strains of Lactobacillus plantarum and Acetobacter orientalis bacteria, and on creating an optimized sugar based medium that could serve as a basis for the development of novel fermented beverages. Previously, in company Heineken they tested both strains for the production of fermented beverages using natural substrates such as barley wort and apple juice. However, natural substrates are quite complex and can vary in composition between different batches, potentially affecting the fermentation process and causing variations in the final products. Therefore, we developed and optimized a novel sugar-based medium that is more defined than natural substrates. The goal of the optimization was to reduce the cost of the sugar medium, produce a higher concentration of the target organic acid in the product (lactic acid with L. plantarum and gluconic acid with A. orientalis), and improve the sensory properties of the fermented sugar medium. We approached the optimization of the medium by testing different concentrations of components in the medium- Na3-citrate, KH2PO4, yeast nutrient type and concentrations, MgSO4, MnSO4 and sugar. We studied the fermentation dynamics of the strains in sugar media with varying compositions to gain deeper insights into their fermentation properties. The parameters analyzed included medium acidification, production of target organic acids, sugar consumption, biomass production and the sensory properties of the final product. Additionally, we examined the production of 2-ketogluconate in A. orientalis. We successfully developed optimized sugar media specifically tailored for the fermentation of L. plantarum and A. orientalis, which are cheaper than the initial formulations and exhibit improved sensory properties after fermentation. Selected sugar media formulations were also scaled up for fermentation, with pilot-scale trials conducted at 1400 L for L. plantarum and at both 0.75 L and 7 L for A. orientalis.

• Language: English
• Keywords: fermented beverages, novel product development, fermentation, bioreactors, acetic acid bacteria, lactic acid bacteria, sugar-based medium, medium optimization, gluconic acid, lactic acid, 2-ketogluconate
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Publisher: [B. Raner]
• Year: 2025
• PID: 20.500.12556/RUL-169280
• UDC: 663.8+663.15:579.67
• COBISS.SI-ID: 237117187
• Publication date in RUL: 22.05.2025

Secondary language

• Language: Slovenian
• Title: Proučevanje fermentacijskih lastnosti ocetnokislinskih in mlečnokislinskih bakterij za razvoj novih pijač na sladkorni osnovi

Abstract

Fermentirani izdelki so splošno znani po prehranskih koristih in potencialno pozitivnih učinkih na zdravje. V zadnjem času se med potrošniki povečuje zanimanje za nove fermentirane pijače, kar predstavlja priložnost za živilsko industrijo, da razišče alternativne substrate in mikroorganizme za proizvodnjo novih fermentiranih pijač. Pri naših raziskavah smo se osredotočili na proučevanje fermentacijskih lastnosti dveh izbranih sevov bakterij, Lactobacillus plantarum in Acetobacter orientalis, in na optimizacijo sladkornega substrata, ki bi lahko služil kot osnova za razvoj novih fermentiranih pijač. V podjetju Heineken so predhodno že preizkusil oba izbrana seva za proizvodnjo fermentiranih pijač iz naravnih substratov, kot sta pivina iz ječmena in jabolčni sok. Vendar so naravni substrati kompleksni in se lahko po sestavi razlikujejo med različnimi serijami, kar lahko vpliva na proces fermentacije in povzroči razlike v končnih izdelkih. Zato smo razvili in optimizirali nov sladkorni substrat, ki je bolj definiran kot naravni substrati. Cilj optimizacije je bil znižati stroške sladkornega substrata, proizvesti višjo koncentracijo ciljnih organskih kislin v izdelku (mlečna kislina z L. plantarum in glukonska kislina z A. orientalis) in izboljšati senzorične lastnosti fermentiranega sladkornega substrata. K optimizaciji substrata smo pristopili s testiranjem različnih koncentracij sestavin v substratu – Na3-citrat, KH2PO4, vrsta in koncentracija kvasnih hranil, MgSO4, MnSO4 in sladkor. Pri fermentacijah različnih sestav sladkornega substrata smo si prizadevali nadalje razumeti fermentacijske lastnosti proučevanih sevov in razumeti, kakšen razpon fermentiranih sladkornih osnov lahko proizvedejo. Analizirani parametri so vključevali zakisanje substrata, proizvodnjo ciljnih organskih kislin, porabo sladkorja, proizvodnjo biomase in senzorične lastnosti končnega izdelka. Pri A. orientalis smo določili tudi količino proizvedenega 2-ketoglukonata. Uspelo nam je razviti optimizirane sladkorne substrate, prilagojene posebej za fermentacijo z L. plantarum in A. orientalis, ki so cenejši od izhodiščnega substrata in imajo po fermentaciji boljše senzorične lastnosti. Fermentacijo optimiziranih sladkornih substratov smo izvedli tudi v pilotnem merilu, in sicer 1400 L z L. plantarum ter 0.75 L in 7 L z A. orientalis.

• Keywords: fermentirane pijače, razvoj novih izdelkov, fermentacija, bioreaktorji, ocetnokislinske bakterije, mlečnokislinske bakterije, sladkorni substrat, optimizacija substrata, glukonska kislina, mlečna kislina, 2-ketoglukonat