Izraba odpadne kisle sirotke za proizvodnjo bakteriocinov z laktokoki

magistrsko delo

Nika Lekan (Author), Barbara Jeršek (Reviewer), Bojana Bogovič Matijašić (Mentor)

Abstract

Raziskovali smo možnost uporabe kisle sirotke iz proizvodnje skute kot substrata za gojenje mlečnokislinskih bakterij vrste Lactococcus (Lc.) lactis, ki proizvajajo bakteriocin nizin. Z merjenjem optične gostote pri 630 nm smo po 20 in 40 urah inkubacije ugotavljali rast laktokokov v bujonu BHI, avtoklavirani in mikrofiltrirani sirotki brez dodatkov ali z dodatki mineralov in/ali kvasnega ekstrakta (5 %). V supernatantih kultur smo merili protimikrobno aktivnost proti indikatorskemu sevu Lactobacillus (L.) sakei subsp. sakei ATCC 15521. Izbrani sevi laktokokov so bili sposobni rasti v osiromašeni kisli sirotki, njihova rast ter proizvodnja bakteriocinov pa se je izboljšala predvsem z dodatkom kvasnega ekstrakta. Spremljali smo tudi obstojnost bakteriocinov v liofiliziranih supernatantih kultur, uravnanih na vrednosti pH 3 ali 6, med 1-mesečnim shranjenjevanju pri različnih temperaturah (sobna temperatura, 4 ºC ali – 20 ºC). Protimikrobno delovanje liofiliziranega nizina se je bolje ohranilo v kislem okolju (pH=3), medtem ko temperatura hranjenja ni imela vidnega vpliva. Nizin iz supernatantov kultur smo delno očistili s precipitacijo z amonijevim sulfatom, ga skoncentrirali z ultrafiltracijo in detektirali z NaDS-PAGE elektroforezo, RP-HPLC in difuzijskim testom z indikatorskim sevom L. sakei subsp. sakei ATCC 15521.

Keywords

mleko;stranski proizvodi;sirotka;kisla sirotka;uporaba sirotke;mlečnokislinske bakterije;Lactococcus lactis;bakteriocini;nizin;protimikrobno delovanje;

Data

Language:	Slovenian
Year of publishing:	2020
Typology:	2.09 - Master's Thesis
Organization:	UL BF - Biotechnical Faculty
Publisher:	[N. Lekan]
UDC:	637.344:579.864.4:615.331
COBISS:	22083587
Views:	672
Downloads:	227
Average score:	0 (0 votes)
Metadata:

Other data

Secondary language:	English
Secondary title:	Use of waste whey for the cultivation of bacteriocin producing lactococci
Secondary abstract:	The aim of the study was to examine the possibility to use acid whey derived from fresh curd cheese as a substrate for the cultivation of lactic acid bacteria of Lactococcus (Lc.) lactis species producing bacteriocin nisin. By measuring the optical density at 630 nm we determined the growth of lactococci in BHI broth, autoclaved and microfiltered whey without supplements or supplemented with minerals and / or yeast extract (5 %), after 20 and 40 hours of incubation. In the culture supernatants we determined the antimicrobial activity against the indicator strain of Lactobacillus (L.) sakei subsp. sakei ATCC 15521. Selected lactococci strains were able to grow in acid whey depleted of proteins, and their growth and bacteriocin production was improved especially with the addition of yeast extract (5 %). We also monitored the stability of bacteriocins in the lyophilized culture supernatants, adjusted to pH 3 or 6, during 1-month storage at different temperatures (room temperature, 4 º C or – 20 º C). The antimicrobial activity of freeze-dried nisin was better preserved in acidic environment (pH = 3), while the storage temperature had no visible effect. The nisin from the culture supernatants was partially purified by precipitation with ammonium sulfate, concentrated by ultrafiltration and detected by SDS-PAGE electrophoresis, RP-HPLC and agar diffusion test, using an L. sakei subsp. sakei ATCC 15521 indicator strain.
Secondary keywords:	milk;by-products;whey;acid whey;whey use;lactic acid bacteria;Lactococcus lactis;bacteriocins;nisin;antimicrobial activity;
Type (COBISS):	Master's thesis/paper
Study programme:	0
Embargo end date (OpenAIRE):	1970-01-01
Thesis comment:	Univ. v Ljubljani, Biotehniška fak., Oddelek za živilstvo
Pages:	IX, 40 f., [4] str. pril.
ID:	11882711