This research presents a mathematical model for routing that incorporates multiple depots, occasional drivers, and multiple depot visits, a problem faced by many companies in reality. An Adaptive Large Neighborhood Search (ALNS) algorithm was employed, using Random and Worst removal operators, Basic Greedy and Regret-2 insertion strategies, a roulette wheel for operator selection, and simulated annealing for acceptance criteria. Computational experiments validated the effectiveness of the ALNS algorithm and model.Sensitivity analysis revealed that adding depots (ODs) can reduce routing costs by up to 15.21%, with various OD capacities offering additional savings (7.86% for 60% capacity and 9.97% for 70% capacity). A case study with the Dutch e-commerce company Ochama, scaled to 150 requests, confirmed practical applicabil- ity, achieving cost reductions of 11.37% for small vehicles and 6.85% for medium-sized vehicles. The results highlight that integrating ODs into routing strategies can significantly lower costs, with optimal outcomes dependent on market research to balance savings, service quality, and OD capacity.

Uronic acid in extracellular polymeric substances is a primary but often ignored factor related to the difficult hydrolysis of waste-activated sludge (WAS), with alginate as a typical polymer. Previously, we enriched alginate-degrading consortia (ADC) in batch reactors that can enhance methane production from WAS, but the enzymes and metabolic pathway are not well documented. In this work, two chemostats in series were operated to enrich ADC, in which 10 g/L alginate was wholly consumed. Based on it, the extracellular alginate lyase (∼130 kD, EC 4.2.2.3) in the cultures was identified by metaproteomic analysis. This enzyme offers a high specificity to convert alginate to disaccharides over other mentioned hydrolases. Genus Bacteroides (>60%) was revealed as the key bacterium for alginate conversion. A new Entner-Doudoroff pathway of alginate via 5-dehydro-4-deoxy-d-glucuronate (DDG) and 3-deoxy-d-glycerol-2,5-hexdiulosonate (DGH) as the intermediates to 2-keto-3-deoxy-gluconate (KDG) was constructed based on the metagenomic and metaproteomic analysis. In summary, this work documented the core enzymes and metabolic pathway for alginate degradation, which provides a good paradigm when analyzing the degrading mechanism of unacquainted substrates. The outcome will further contribute to the application of Bacteroides-dominated ADC on WAS methanogenesis in the future.

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