Jingwei Geng (1), GUANGTIAN ZHOU (1), Xiaolei Dong (1), Yunqian Cui (1)
(1) Shandong Provincial Key Laboratory of Microbial Engineering, Shandong Institute of Light Industry, Jinan, Shandong, China
Previous studies in our laboratory have shown that 10-hydroxy-2-decenoic acid (10-HDA) displayed antimicrobial effect on G+ beer-spoilage bacteria Lactobacillus brevis and Pediococcus damnosus. In the present report, we studied the inhibitory effect of 10-HDA on typical G+ beer-spoilage bacteria Pectinatus spp.
and wild yeasts. We also studied whether 10-HDA could be used in
top-fermented wheat beer as a food additive and as an antimicrobial
agent. 10-HDA was extracted from royal jelly with ethanol. The
extraction efficiency was detected by high-pressure liquid
chromatography (HPLC). The process of extraction was optimized using
orthogonal experiments. The antimicrobial effect of 10-HDA on two
strains of bacteria and three strains of yeasts was determined by
inhibition zone experiments and flow cytometry assay. The antibacterial
effect of iso-α-acid on these microorganisms was detected synchronously.
The Oxford cup assay was used to determine the minimum inhibitory
concentration (MIC) of 10-HDA by double dilution method. The results
showed that 10-HDA could significantly inhibit Candidamy coderma, Pectinatus cerevisiiphilus, and Pectinatus frisingensis. No inhibition effect was found while treating top-fermenting yeast No. 303 and Saccharomyces diastaticus
with 10-HDA. Similar antibacterial effects were obtained while using
the flow cytometry test. In contrast, iso-α-acid only inhibited the
growth of Candidamy coderma with MIC at a concentration of 62.5 mg/L. However, no inhibition effect was found when Pectinatus spp.
was treated with iso-α-acid. 10-HDA was added to the top-fermented
wheat beer with the bitterness 20.25 mg/L. The antimicrobial effect of
10-HDA in this kind of beer was determined by NBB culture medium test
and microorganism index analysis. The results showed that the 10-HDA
displayed potent antibacterial effects while being used as a food
additive in top-fermented wheat beer and the inhibitory effect of 10-HDA
in top-fermented beer is not related to iso-α-acid. Our study provided
evidence that 10-HDA could be developed as a novel antimicrobial agent
in top-fermented wheat beer.
Guan
gtian Zhou is a professor in bioengineering, and also a director
of the China-Germany Brewing Technical Service Center in the Shandong
Institute of Light Industry. Guangtian received his B.S. degree in
bioengineering from the Shandong Institute of Light Industry in Jinan,
China. He worked in the Jinan Beer Group from 1982 to 1987 as a brewer.
From 1987 until 1988, he studied at Doemens Brewing Akademie in Munich,
Germany, as a scholar. He then worked in the Jinan Beer Group as a chief
engineer. Since 1994, he has been working in the Shandong Institute of
Light Industry as a professor. He is now the director of the
China-Germany Brewing Technical Service Center. Guangtian is also an
editor of China Brewing, a famous journal in China, and a council member of the Microorganism Association of Shandong, China.
VIEW PRESENTATION
