Instead of tea with sugar: soybean molasses helped tea fungus to produce more bacterial cellulose.

Newswise — Scientists tested different methods of obtaining bacterial cellulose on the base of tea fungus. It turned out that when they grow on soybean molasses, microorganisms produce more by 57% of this product than on the base of tea with sugar. This method will make the production cheaper, because soybean molasses is a by-product of soybean processing, that is obtained in great amount at factories. Thanks to such cheap and accessible substrate it will be possible to produce bacterial cellulose, that is used in medicine for wound healing and neogenesis, industrially. Results of the research supported by the grant of Russian Scientific Foundation (RSF), are published in the magazine Food Science and Technology.

Bacterial cellulose is a biopolymer that is in demand in medicine, cosmetology, tissue engineering and other fields. It is also used for production of fuel and explosives, cosmetic products and also dressings that speed wound healing. The so-called tea fungus — a symbiotic colony of yeast and lactic acid and acetic bacteria — is thought to be the most effective “producer” of bacterial cellulose. However, to obtain a great volume of bacterial cellulose you have to incubate microorganisms on complex and expensive breeding grounds. Thus, to make the production cheaper scientists are looking for alternatives, for example, breeding grounds on the base of cheap plant raw material.

Biotechnologists from Immanuel Kant Baltic Federal University (Kaliningrad), National Research University ITMO (Saint Petersburgh) and Kemerovo State University (Kemerovo) suggested to use soybean molasses, the by-product of soybean processing, as a substrate (growth medium) for tea fungus. Annually 1,58 million tons of soybean molasses is produced and utilized in Russia.

In order to understand which conditions enable to obtain maximal amount of bacterial cellulose authors tested 5 variants of breeding grounds: tea with sugar, soybean molasses with tea and sugar, soybean molasses with sugar, soybean molasses with tea and pure soybean molasses. Scientists chose tea as “control” breeding ground because it is often used for growing of tea fungus. In order to make microorganisms to produce bacterial cellulose, additional concentrates, such as glucose, yeast extract and peptone are usually added to tea. As a result, breeding ground becomes expensive, besides this, it is possible to obtain not much product on its base, that makes cost of production also grow.

After 20 days of experiment in cultures formed hard films of bacterial cellulose. It turned out that in the breeding ground from soybean molasses, sugar and tea microorganisms grow better than on tea with sugar. Moreover, yield of bacterial cellulose, obtained on the control ground (tea with sugar) was by 49% and 37% lower according to temperature od cultivation. It tells about the fact that soybean substrates are an excellent breeding ground, that helps more active reproduction of microorganisms and productive cultivation.

Besides this, biologists compared growth of two variants of tea fungus — natural and laboratory ones —  on different breeding grounds. Microbial communities differed with one another as far as species composition is concerned. Thus, natural tea fungus includes community of yeasts and bacteria Medusomyces gisevii. The laboratory variant has modified community, that includes acetic-acid bacteria Komagataeibacter sucrofermentans, lactic-acid microorganisms Lactobacillus sakei and Streptococcus thermophilus, and also yeasts Pachysolen tannophilus. Authors combined these strains in proportion 4:3:1. After that they mixed them with natural “tea fungus”, and so obtained the modified variant of tea fungus.

Although natural tea fungus is less fastidious by growing and doesn’t require sterility, laboratory modified variant turned out to be a better producer of bacterial cellulose. Thus, during its growing in breeding ground with soybean molasses the maximal yield of bacterial cellulose increased by 56-58% as compared with natural group of microorganisms.

The suggested approach can become economical technology of production of bacterial cellulose, because it uses available waste of food industry as a breeding ground for growing of microorganisms. It helps to reduce costs by 50% and get great volumes of biopolymer.

“In order to understand mechanisms of formation of bacterial cellulose better, it is necessary to continue a further investigation how to obtain it on alternative breeding grounds, the base of which is formed by waste of agro-industrial complex or low-value plants, for example, cane molasses, orange and pineapple juices and peeling, acid hydrolysate and others”, - tells the head of the project, supported by the grant of RSF, Olga Krieger, Doctor of Engineering, professor of ITMO University's Faculty of Biotechnologies.