Cosmetics from orange peel

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In a natural bioprocess, bacteria can convert limonene into perillic acid. Source: Schrader / Dechema e. V.

22.03.2011  - 

Every year, Brazil produces 1.25 million litres of orange juice concentrate. The manufacturing process also creates a little used natural by-product known as limonene. Scientists at the Zwingenberg-based biotech company BRAIN in cooperation with researchers from the Dechema Society for Chemical Engineering and Biotechnology are working on a natural preservative based on limonene – with a little help from bacteria. The project is being supported by the Federal Ministry of Education and Research (BMBF).

Take a look at the supermarket shelves, and you’ll see hand creams “fortified with precious sea buckthorn oil” or toothpaste with extracts of “Rathania roots from the Peruvian Andes.”  Products such as these have been high in demand in recent years. Indeed, marketing research firm Information Resources Inc. concludes that the share of natural cosmetics in the overall market increased from 3.8% to 5.4% between 2008-2010. Last year, sales in this area grew by 15%, despite shrinking turnover for conventional cosmetics.

Against this backdrop, it’s no surprise that cosmetic manufacturers are increasingly on the lookout for ingredients with natural origins. This is also true for preservatives that help to give skin creams a longer shelf life. Most creams are chemically produced, and some such as benzyl benzoate are considered by experts to be the cause of allergic reactions.

Thousands of tons of lime unused

Researchers have long been searching for a way of replacing such substances with natural products. Years ago, researchers led by Jens Schrader of Dechema’s Karl Winnacker Institute together with the company Dr. Riek GmbH have developed a procedure that uses as its basis a natural product made from orange peel. About 50,000-75,000 tons of the substance limonene is produced as a by-Productin industries dealing with citrus fruits. This is a natural liquid substance from the terpene group, found in lemons and oranges and other essential oils. It has been little used to date in other products or processes. In a project funded by the German Federal Environmental Foundation (DBU), the researchers have demonstrated in principle that the preservative perillic can be naturally produced from limonene using the bacterium Pseudomonas putida. In the meantime, the patents for the process have passed over to the biotech company BRAIN AG, which specialises in the development of biotechnological processes for industry, and whose founder Holger Zinke is regarded as a pioneer of white biotechnology (more...).

In industrial production, these beneficial bacteria are grown in gigantic fermenters. The biotechnological processes occur in the steel tanks.Source: Brain AG

Schrader and the researchers at Brain now want to further optimise the process on the basis of limonene for industrial production. They are being supported until 2012 by the Federal Ministry of Education and Research as part of the GenoMik funding initiative.

With the program ‘Industrial production processes for novel enzymes and bioactive substances from natural sources: MikroPro’, which has been ongoing since 2007, the biotechnologists in Zwingenberg are hoping to bring biotechnological research from the laboratory to industrial application. Brain has invested a total of around 5.8 million euros in the development programme over a period of five years. This includes € 2.8 million in BMBF grants exclusively for pre-competitive basic research. Among others, the perillic acid project is now set to benefit from this support.

Perillic acid: toxic for bacteria

No small amount of research work will be required until the process is actually ready for industrial application. The problem is that the bacterium Pseudomonas putida can happily tolerate the starting material limonene, but the end product perillic acid in its high concentration in the bioreactor interferes with the bacterial growth. Naturally occurring perillic acid in plants has a strong antimicrobial effect, i.e. most microbes are significantly less able even than Pseudomonas to tolerate perillic acid.

Developing a biotechnological process for industry on this basis will be no easy task. In the meantime, the scientists have succeeded in stopping Pseudomonas putida from halting the perillic acid production entirely with its antimicrobial ways. Thereby, the bacteria are continuously supplied with sufficient limonene, while the resulting perillic acid is continuously removed from the bioreactor. On a small scale, this process is already working well, but now the focus is on producing larger quantities.

Many improvements will have to be made until the substance really takes hold in the many pots and bottles of the cosmetics industry. “We want to optimise the production process to such an extent that perillic acid is approved as an ingredient for the cosmetics industry,” said Stefan Pelzer, who manages the project at Brain. In the medium term, there will be a clear division of labour: Schrader’s researchers will take care of the further technical optimisation and the ‘upscaling’ – the stages that take production from the laboratory to far larger industrial plants. The scientists at Brain are focusing on all the factors that relate to the approval of natural perillic acid. This involves, for example, ensuring that the bacteria's natural preservatives are produced with a consistent quality and with as few by-products as possible. This could take until 2012, however, estimates Pelzer. If it indeed succeeds, the researchers believe that perillic acid from bacteria will have a bright future in the cosmetic industry. “For example, one day you could find the substance in anti-dandruff shampoos,” says Pelzer. There, the perillic acid could kill off those microbes that are responsible for the formation of the scaly flakes.