Electroplating generates high volumes of rinse water that is contaminated with heavy metals. This study presents an approach for direct metal recovery and recycling from simulated rinse water, made up of an electroplating electrolyte used in industry, using reverse osmosis (RO). To simulate the real industrial application, the process was examined at various permeate fluxes, ranging from 3.75 to 30 L·m−2·h−1 and hydraulic pressures up to 80 bar. Although permeance decreased significantly with increasing water recovery, rejections of up to 93.8% for boric acid, >99.9% for chromium and 99.6% for sulfate were observed. The final RO retentate contained 8.40 g/L chromium and was directly used in Hull cell electroplating tests. It was possible to deposit cold-hued chromium layers under a wide range of relevant current densities, demonstrating the reusability of the concentrate of the rinsing water obtained by RO.
Commercial baker's yeast—a low-cost product with a low profit margin—requires complex fermentation techniques (large-scale, fed-batch fermentation) and is subject to strict quality safety regulations. Large amounts of molasses, ammonia, and vitamins, as well as air and water (liquid and steam) are necessary for the efficient industrial production of baker's yeast. The associated production costs are strongly correlated to the increasing and volatile market price for molasses. In this regard, producers mainly concentrate their efforts on the search for alternative sugar sources and the further improvement of bioprocess control and efficiency. As industrial baker's yeast production has been optimized over many decades, there is only little room left for such improvements. New, interesting trends regarding baker's yeast production have been recently drafted by different research groups and are reviewed in this paper. Subsequently, we combined these multidisciplinary advances in an innovative strategic concept and demonstrated how industrial baker's yeast biomanufacture can be turned into a powerful, zero-discharge multipurpose bioprocess. As a result, the redesigned bioprocess provides a large amount of district heat as well as key molecules such as invertase and betaine. It uses side streams from the food industry as carbon and nitrogen sources and strongly relies on state-of-the-art membrane technology. The presented approach aims to show how industrial aerobic processes can be employed within a sustainable industrial environment.
The objectives set in the European Green Deal constitute the starting point of this review, which then focuses on the current implementation gap between agro-industrial wastes as resources for large-scale bioprocesses (e.g., baker’s yeast, bioethanol, citric acid, and amino acids). This review highlights the current lack of sustainability of the post-harvest processing of grapes and apples. In light of the European Green Deal, industrial biotechnology often lacks sustainability as well. We reviewed the recent progress reported in the literature to enhance the valorization of grape and apple pomace and the current failure to implement this research in technical processes. Nevertheless, selected recent papers show new perspectives to bridge this gap by establishing close collaborations between academic teams and industrial partners. As a final outcome, for the first time, we drew a circular flow diagram that connects agriculture post-harvest transformation with the industrial biotechnology and other industries through the substantial valorization of apple and grape pomace into renewable energy (solid biofuels) and sugar extracts as feedstock for large-scale bioprocesses (production of baker’s yeast industry, citric acid, bioethanol and amino acids). Finally, we discussed the requirements needed to achieve the successful bridging of the implementation gap between academic research and industrial innovation.