Harvesting can contribute up to 15% of the total production cost for microalgal biomanufacturing. Using flocculants is potentially a cost-effective approach but there has been considerable debate on the efficacy, cost, toxicity to the cell and environment, and the effect on the biomass further downstream. In this study, a range of biobased flocculants (chitosan from crab shells, Moringa oleifera seed extract, pectin from bananas, tannic acid-based derivatives from Acacia tree bark and egg shell powder) were compared with traditional chemical flocculants (aluminium sulphate, iron chloride and sodium hydroxide) for harvesting the diatom Phaeodactylum tricornutum. It was concluded that Tanac’s tannin based Tanfloc 8025 (SL range) was the most promising, requiring a low concentration (10.4 kg ton⁻¹ biomass), at low cost ($27.04 ton⁻¹ microalgal biomass). The flocculant was effective over a wide pH (7.5–10.0) and temperature (15–28 °C) range and harvesting (>85% efficiency) occurred in 10 mins, which resulted in a biomass concentration factor of ≥ 5.69.

收获可占微藻生物制造总生产成本的15％。使用絮凝剂可能是一种具有成本效益的方法，但是在功效，成本，对细胞和环境的毒性以及对下游生物质的影响方面存在很多争论。在这项研究中，将一系列生物基絮凝剂（蟹壳的壳聚糖，辣木种子提取物，香蕉的果胶，金合欢树皮的单宁酸衍生物和蛋壳粉）与传统的化学絮凝剂（硫酸铝，氯化铁）进行了比较。和氢氧化钠）收获硅藻Phaeodactylum tricornutum。结论是，Tanac基于单宁的Tanfloc 8025（SL系列）是最有前途的，需要低浓度（10.4 kg吨^-1生物量）和低成本（27.04吨^-1微藻生物量）。絮凝剂是在宽的pH（7.5-10.0）和温度（15-28℃）范围内和收获（> 85％的效率）有效发生在10分钟，这导致的生物量浓度因子 ≥  5.69。