Macaúba ( Acrocomia aculeata ) pulp oil ethylic biodiesel using lipase from Aspergillus oryzae : kinetic and process parameters

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Abstract Macaúba ( Acrocomia aculeata ), a native species from Brazilian biomes, has emerged as a sustainable alternative to vegetable oil production. Its fruit presents high oil yield (3–6 ton/ha), extracted from its kernel and pulp. While the kernel is suitable for food and cosmetics application, the pulp oil has been considered as a promising feedstock for biodiesel production, aligned to the Brazilian National Biofuels Policy. Despite this biofuel being widely produced through chemical routes and methanol, the use of lipases, such as commercial lipase produced from Aspergillus oryzae (Eversa Transform 2.0), has been described as a more sustainable alternative, allowing the use of crude oils, among other advantages. In this case, the use of ethanol from sugarcane can also replace methanol, additionally improving the process's environmental performance. In this context, this work evaluated kinetic and optimal process parameters for the production of ethyl biodiesel from Macaúba pulp oil using the Aspergillus oryzae lipase. The kinetic study could incorporate both transesterification and esterification mechanisms, characteristic of this lipase. A central composite rotational design at fixed temperature (40 °C) was applied to determine the best operational conditions, estimated in the region close to mild ethanol‐to‐oil molar ratio (4.5) and upper limits of enzyme (m/m oil ) and water (m/m oil ) (2.0% and 4.0%), allowing conversions higher than 95%. The results showed that ethanol is strategic when compared to methanol, allowing their addition in a single step without lipase inactivation. On the other hand, final residual acidity was found to be a bottleneck in the lipase action mechanism, demanding further purification steps. The results revealed that this lipase is an efficient strategy for ethyl biodiesel production using crude or lightly pre‐treated oils, allowing high conversion while presenting advantages over the use of alkalis or acids.

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