Sabtu, 17 Oktober 2009

Biosurfaktan dari Rhodococcus erythropolis

Biossurfaktan adalah molekul amfipatik yang dapat dibedakan dalam senyawa dengan berat molekul rendah seperti glikolipid, fosfolipid dan lipopeptida dan surfaktan dengan berat molekul tinggi seperti polisakarida, protein, lipoprotein atau biopolymer kompleks lainnya (Rosenberg and Ron. 1990).

Biosurfaktan memiliki aplikasi yang menarik karena sifat-sifat fungsionalnya yang luas termasuk di dalamnya kemampuan dalam pembersihan, pembasahan, pembuihan, emulsifikasi, reduksi viskositas, pemisahan dan pelarutan. Kemampuan tersebut banyak dimanfaatkan dalam industri pembersih, pertanian, konstruksi, pangan, kertas, industri logam, tekstil, kosmetik, farmasi dan industri petrokimia termasuk dalam aplikasi di lingkungan untuk bioremediasi. Biosurfaktan memiliki kelebihan karena mudah didegradasi, toksisitasnya rendah, dan dapat dihasilkan dari substrat yang bernilai ekonomi rendah ataupun limbah (Banat, Makkar., and Cameotra. 2000).

Surfaktan dihasilkan oleh berbagai mikrobia (bakteri dan jamur), sebagai produk ekstraselular terutama jika ditumbuhkan pada n-alkana atau yang sejenis. Namun demikian, beberapa surfaktan microbial dapat dihasilkan pada substrat yang larut air (Fiechter. 1992).

Rhodococcus erythropolis mampu menghasilkan biosurfaktan saat ditumbuhkan pada gliserol dengan suhu 280C. Biosurfaktan yang dihasilkan setelah 51 jam penumbuhan adalah sebesar 1,7 g/L dengan tegangan muka sebesar 43 mN/m dan tegangan permukaan (dengan n-heksadekana) sebesar 15 mN/m, indeks emulsifikasi (E24), dan minyak yang dapat dihilangkan 94 %. Penggunaan gliserol lebih baik dalam produksi gliserol dibandingkan sumber karbon hidrofobik (Ciapina, et al. 2006).

Rabu, 05 Agustus 2009

Oxo-bio industry says product claims valid

By Rory Harrington, 04-Aug-2009

An oxo-biodegradable industry body has refuted charges made by a rival association that its products fail to meet valid or recognised standards, and that the sector has yet to present sound scientific evidence to support its claims.

The Oxo-Biodegradable Plastics Association (OPA) has said the standards it uses to verify the biodegradability of its products are legitimate and that claims made by the industry are founded on solid science.

Recognised standards

Gerald Scott, Professor Emeritus in Chemistry and Polymer Science of Aston University and OPA Chairman, has rejected a series of charges laid against the sector by competitor European Bioplastics (EP).

In its second attack on the oxo-bio segment, EP said the American Standard ATSM D-6954-04 was not an acknowledged standard. Furthermore, it questioned the validity of citing the test because it had no pass/fail criteria but simply described how to operate tests in the laboratory.

But Scott, who is also chairman of the British Standards Institute Committee on Biodegradability of Plastics, said EP's accusation was incorrect.

"It is impossible to say that ATSM D6954 is not an acknowledged standard," he told "It not only provides detailed test methods but also provides pass/fail criteria."

The retired professor gave para 6.6.1 as an example that requires 60 per cent of the organic carbon must be converted to carbon dioxide prior to the end of the test and that gel content must be no higher than 10 per cent.

EB had also criticised use of the standard as it did not comply with EN13432, used by its own members, that sets a deadline for this to occur within 180 days. But Scott said there was no requirement for the 60 per cent conversion to be achieved in this time because, while timescale was critical in an industrial composting process, it was not critical for biodegradation in the environment. He said that for EB to compare the two standards did not make sense as they tested for different things; compostability in the case of EN 13432, while ASTM checked biodegradability.

"The issues raised by EB are not about clarification- they seem to me an attempt to confuse the public by suggesting a plastic is not biodegradable unless it can pass the 90 per cent mineralization test in EN 13432 and similar standards," said Scott . "EB knows perfectly well that this test is appropriate for composting but not for products designed to biodegrade in the environment."

Independent tests but results confidential

The OPA chairman also dismissed EP charges that the oxo-bio sector made "self-declared" claims, saying the products were subject to independent testing and their validity based on well-established science. The tests were conducted according to ASTM D-6954 by independent laboratories such as US and UK-based Smithers-RAPRA, Applus in Spain and Belgian testers OWS, said the body citing a number of examples.

Oxo-bio products degrade according to the definition as those "breaking down to a specific extent within a given time", said Scott in contradiction to another EB claim. He said that oxo-bio products meet definitions of oxo-degradation and oxo-degradability as defined by TC249/WG9 of CEN (the European Standards Organisation).

Scott said he had seen commercially confidential company reports verifying performance on degradability.

'I am satisfied that if properly manufactured oxo-bio products will totally degrade in the presence of oxygen," he added. "Timescale depends on the amount of heat, light and stress to which the materials is subjected."


EB claims that oxo-bio products could only be degraded under laboratory conditions after a pre-treatment were dismissed as irrelevant by the rival organisation.

Scott said that conditions in the laboratory were designed to simulate, so far as possible, conditions in the real world but had to be accelerated so tests could be done in a reasonable time.

"Pre-treatment does not invalidate the results as extrapolated to real-world conditions," he said.