Fisiologie van Sporolactobacillus

Abstract

Sporolactobacillus-isolate is verkry vanaf die mis van verskillende herbivore diere, asook vanaf die rumen van 'h bees en die finale afvloeiwater van 'h abattoir. Die isolate toon onderlinge verskille ten opsigte van hulle morfologiese en fisiologiese eienskappe. Een isolaat (L2404) het selfs verskil ten opsigte van die karakteristieke eienskap waarop die spesienaam van Sporolactobacillus inulinus berus, naamlik die vermoe om inulien te fermenteer. Die gemiddelde minimum-, maksimum- en optimum pH-waardes vir groei van Sporolactobacillus was 3,5, 8,0 en 6,5-7,0 onderskeidelik. Die weerstandbiedendheid van Sporolactobacillus teen chemiese preserveermiddels soos natriumni triet en kaliumsorbaat was relatief haag. Spoorontkieming en groei van Sporolactobacillus het plaasgevind -1 tot 'h konsentrasie van 2000 mg.Q natriumnitrie~ geen minimum inhiberende konsentrasie waarby natriumnitriet spoorontkieming en groei volledig geinhibeer het, kon in hierdie studie vir Sporolactobacillus aangedui word nie. Die minimum inhiberende konsentrasie kaliumsorbaat wat spoorontkieming en groei van spore sowel as vegetatiewe selle van Sporolactobacillus inulinus ATCC -1 15538 volledig onderdruk het, was 4000 mg.Q kaliumsorbaat. Vir die isolate van Sporolactobacillus het die minimum inhiberende konsentrasies vir volledige inhibisie van spoorontkieming en groei (5000 mg.Q- 1 ) verskil van die vir vegetatiewe groei (7000 mg.Q- 1 ). Spoorontkieming en groei van Sporolactobacillus vind by relatief lae aw-waardes plaas en die minimum aw-waarde vir spoorontkieming en groei was ongeveer 0,88 as aw met gliserol ingestel is. NaCl as voghouer het 'h toksiese effek (addisioneel tot die inhibisie deur aw-verlaging) op spoorontkieming en groei gehad, terwyl volledige inhibisie by 'h aw-waarde van 0,956 gevind is. Die. y D10 -waarde vir spore van Sporolactobacillus-isolate in GYP-sop was gemiddeld 2,5 kGy en vir vegetatiewe selle 0,35-0,525 kGy • Die antagonisms van 'h Sporolactobacillus-isolaat, L2407, teen spesifieke 8acillus-spesies, kan moontlik aan die produksie van bakteriosien en/of 'h ander antagonistiese produk toegeskryf word. Alhoewel laboratoriumondersoeke getoon het dat spore van Sporolactobacillus by lae aw-waardes (<0,94) kan ontkiem en groei, ken geen aktiewe spoorontkieming en groei in eksperimentele rakstabiele produkte aangedui word nie. Die verskynsel kan waarskynlik toegeskryf word aan die interaksie van verskillende faktore wat in die produk teenwoordig is.Positive isolation of Sporolactobacillus was made from the faeces of different herbivores, as well as from the rumen of cattle and the final waste water of an abattoir. The isolates showed differences concerning their morphological and physiological properties, and one isolate (L2404) differed by its inability to ferment inulin, which is an essential characteristic for allocation of an isolate to the .species Sporolactobacillus inulinus. The average minimum-, maximum- and optimum pH-values for growth of Sporolactobacillus were 3,5, 8,0 and 6,5-7,0 respectively. Resistance of Sporolactobacillus to chemical preservatives was relatively high. Germination and outgrowth of spores of Sporolactobacillus takes place at sodium nitrite concentrations as _1 high as 2000 mg.e It was not possible in this study to determine a minimum inhibitory concentration for sodium nitrite, at which germination and growth of spores was completely inhibited. The minimum inhibitory concentration of potassium sorbate that completely inhibited germination and growth of spores as well as vegetative -1 growth of Sporolactobacillus inulinus ATCC 15538 was 4000 mg.e • For the isolates of Sporolactobacillus the minimum inhibitory concentration for germination and growth of spores and for vegetative growth -1 -1 was5u00 mg.e and 7000 mg.e potassium sorbate respectively. Germination and growth of spores of Sporolactobacillus take place at relatively low aw-values. The minimum aw-value where germination and growth of spores took place was approximately 0,88 when aw-values were adjusted with glycerol. NaCl used as humectant for adjusting aw-values appeared to have a toxic effect, in addition to inhibition by reduced aw,on germination and growth of Sporolactobacillus spores. Complete inhibition was found at an aw-value of 0,956. 010 -values for Y-irradiation of spores of Sporolactobacillus strains in GYP-broth averaged 2,5 kGy as compared to values between 0,35 and 0,525 kGy for vegetative cells. The antagonistic effect of a Sporolactobacillus isolate, L2407, on specific Bacillus species was probably caused by the production of a bacteriocin and/or another antagonistic substance. Although laboratory experiments showed that the spores of Sporolactobacillus germinate and grow at low a -values (<0,94),no active w germination or growth could be observed in experimental shelf-stable products. This may be attributed to the presence of additional inhibitory factors (or a combination thereof) present in the products. Digitised