Increasing efforts are directed towards the development of sustainable alternative protein sources among which microbial protein (MP) is one of the most promising. Especially when waste streams are used as substrates, the case for MP could become environmentally favorable. The risks of using organic waste streams for MP production-the presence of pathogens or toxicants-can be mitigated by their anaerobic digestion and subsequent aerobic assimilation of the (filter-sterilized) biogas. Even though methane and hydrogen oxidizing bacteria (MOB and HOB) have been intensively studied for MP production, the potential benefits of their co-cultivation remain elusive. Here, we isolated a diverse group of novel HOB (that were capable of autotrophic metabolism), and co-cultured them with a defined set of MOB, which could be grown on a mixture of biogas and H2/O2. The combination of MOB and HOB, apart from the CH4 and CO2 contained in biogas, can also enable the valorization of the CO2 that results from the oxidation of methane by the MOB. Different MOB and HOB combinations were grown in serum vials to identify the best-performing ones. We observed synergistic effects on growth for several combinations, and in all combinations a co-culture consisting out of both HOB and MOB could be maintained during five days of cultivation. Relative to the axenic growth, five out of the ten co-cultures exhibited 1.1-3.8 times higher protein concentration and two combinations presented 2.4-6.1 times higher essential amino acid content. The MP produced in this study generally contained lower amounts of the essential amino acids histidine, lysine and threonine, compared to tofu and fishmeal. The most promising combination in terms of protein concentration and essential amino acid profile was Methyloparacoccus murrelli LMG 27482 with Cupriavidus necator LMG 1201. Microbial protein from M. murrelli and C. necator requires 27-67% less quantity than chicken, whole egg and tofu, while it only requires 15% more quantity than the amino acid-dense soybean to cover the needs of an average adult. In conclusion, while limitations still exist, the co-cultivation of MOB and HOB creates an alternative route for MP production leveraging safe and sustainably-produced gaseous substrates.

中文翻译：

---

通过甲烷和氢气氧化细菌的共培养，从沼气和氢气到微生物蛋白质。

人们越来越多地致力于开发可持续的替代蛋白质来源，其中微生物蛋白质（MP）是最有前途的之一。特别是当废物流被用作底物时，MP 的情况可能变得对环境有利。使用有机废物流进行 MP 生产的风险（病原体或毒物的存在）可以通过其厌氧消化和随后的（过滤消毒的）沼气的有氧同化来减轻。尽管甲烷和氢氧化细菌（MOB 和 HOB）在 MP 生产方面已得到深入研究，但它们共培养的潜在好处仍然难以捉摸。在这里，我们分离出了一组不同的新型 HOB（能够进行自养代谢），并将它们与一组确定的 MOB 共培养，这些 MOB 可以在沼气和 H2/O2 的混合物中生长。MOB 和 HOB 的组合，除了沼气中含有的 CH4 和 CO2 之外，还可以使 MOB 氧化甲烷产生的 CO2 增值。不同的 MOB 和 HOB 组合在血清瓶中生长，以确定性能最好的组合。我们观察到几种组合对生长的协同效应，并且在所有组合中，由 HOB 和 MOB 组成的共培养物可以在五天的培养期间维持。相对于无菌生长，十个共培养物中有五个表现出高出 1.1-3.8 倍的蛋白质浓度，并且两种组合表现出高出 2.4-6.1 倍的必需氨基酸含量。与豆腐和鱼粉相比，本研究中生产的 MP 中必需氨基酸组氨酸、赖氨酸和苏氨酸的含量通常较低。就蛋白质浓度和必需氨基酸谱而言，最有希望的组合是甲基副球菌 LMG 27482 与 Cupriavidus necator LMG 1201。来自 M. murrelli 和 C. necator 的微生物蛋白需要量比鸡肉、全蛋和豆腐少 27-67%，而它只需要比氨基酸密集的大豆多15%的数量就可以满足一个普通成年人的需要。总之，虽然仍然存在局限性，但 MOB 和 HOB 的共培养为利用安全且可持续生产的气态底物进行 MP 生产创造了一条替代途径。