New insight into the role of oxygen supply for surfactin production in bench-scale bioreactors using induced surface aeration.

Surfactin biosurfactant produced by Bacillus sp. has been studied, because it has enormous potential in several applications in the oil and cosmetics industry. The cultivation conditions for obtaining this bioproduct, however, still require attention, as, for example, parameters related to oxygen supply and consumption. In this study, different volumetric oxygen transfer coefficient (KLa) levels (0-11.56 h-1) were tested in bench-scale bioreactor for surfactin biosurfactant production by Bacillus velezensis H2O-1, using induced surface aeration. While conditions close to anaerobiosis showed insignificant production of surfactin, an intermediated KLa condition (4.24 h-1) generated the best surfactin concentration (579.6 mg L-1), with a volumetric productivity of 11.9 mg L-1 h-1. These results showed that the oxygen demand to produce surfactin is not high, being possible to use induced surface aeration strategy in bioreactors, minimizing foam formation. In addition, in all KLa conditions tested, surfactin homologues C14 and C15 had higher relative abundance. Nevertheless, the KLa parameter seems to have had minimal influence on affecting the relative abundances of surfactin homologues produced. Particularly noteworthy in this study is the possibility of producing surfactin using a low-cost and scale-up feasible aeration strategy, unlike the foam collection strategies developed in other studies to obtain this bioproduct.

Environmentally friendly rhamnolipid production for petroleum remediation.

Biosurfactants have potential applications in the remediation of petroleum-contaminated sites. Several strategies can be used to reduce the production costs of these surfactants and make the process more environmentally friendly. In this study, we combined some of these strategies to produce the rhamnolipid-type biosurfactant, including the use of the genetically modified strain Pseudomonas aeruginosa-estA, an industrial coproduct as a carbon source, a simple and low-cost medium, and a simple downstream process. The process resulted in a high yield (17.6 g L-1), even using crude glycerin as the carbon source, with substrate in product conversion factor (YRML/s) of 0.444. The cell-free supernatant (CFS) was not toxic to Artemia salina and selected mammalian cell lineages, suggesting that it can be used directly in the environment without further purification steps. Qualitative analysis showed that CFS has excellent dispersion in the oil-displacement test, emulsifying (IE24 = 65.5%), and tensoactive properties. When salinity, temperature and pressure were set to seawater conditions, the values for interfacial tension between crude oil and water were below 1.0 mN m-1. Taken together, these results demonstrate that it is possible to obtain a nontoxic crude rhamnolipid product, with high productivity, to replace petroleum-based surfactants in oil spill cleanups and other environmental applications.

Extraction of Phenolic Compounds from Palm Oil Processing Residues and Their Application as Antioxidants.

The side streams derived from the palm oil production process, namely palm kernel cake, palm pressed fibre, palm kernel shells and empty fruit bunches, were evaluated as sources of phenolic compounds. Among these streams, kernel cake had the highest total phenolic content (in mg of gallic acid equivalents (GAE) per g of dry sample) with a value of 5.19, whereas the empty fruit bunches had the lowest value (1.79). The extraction time and liquid-to-solid ratio were investigated to optimize the phenolic extraction. Kernel cake exhibited the highest total phenolic content (5.35 mg/g) with a liquid-to-solid ratio of 40:1 during 20 min of extraction. The main phenolic compounds of the extracts deriving from all byproduct streams were also identified and quantified with HPLC-DAD. Pyrogallol, 4-hydroxybenzoic acid, gallic acid and ferulic acid were the main compounds found in kernel cake extracts. Empty fruit bunch and pressed fibre extracts were also rich in 4-hydroxybenzoic acid, while pyrogallol was the predominant compound in kernel shell extracts. All extracts showed antioxidant activity as it was indicated from the results of DPPH analysis and subsequently tested in sunflower oil aiming to prolong its shelf life. The addition of 0.8% kernel cake extract increased the induction time of sunflower oil more than 50%. According to the results obtained in this study, kernel cake extracts could be considered as a value-added co-product with a potential application as antioxidants in the food industry.