Research Excellence

Artificial methods for increasing the yield of food crops have been a hot area of research. Photosynthesis is still the fundamental of how crops interact with the substantial environment and the Mother Nature plays a significant role in the process.However, natural photosynthesis (NPS) has a very low energy efficiency (typically <1%) in producing sugars and starch in plants. Three major limiting factors are the waste of solar energy in the green light being reflected by chlorophylls, low concentration of CO2 in the atmosphere (~420 ppm), and the low activity and poor specificity of central enzyme in NPS (D-ribulose-1,5-bisphosphate carboxylase/ oxygenase (RuBisCO)).

Dr Zhang Xuming, Associate Professor of the Department of Applied Physics, has been developing artificial photosynthesis systems (APS) to convert CO2 into glucose precursors, which could be further processed into food materials. 

In his research, multiple microfluidic platforms mimicking the NPS pathway with scalable microreactors have been built to streamline the light capturing and enzymatic reactions. Visible-absorbing semiconducting photocatalysts (e.g., C3N4, Cu2O, Au/TiO2) have been used to replace chlorophylls for better utilization of solar light and higher durability. He also uses NaHCO3 solution to obtain higher CO2 concentration. Dr Zhang also discovered that the performances of RuBisCO are significant in enhancing enzyme stability and reusability that energy efficiency and enzyme activities can be greatly improved with the use of a very limited amount of RuBisCO.

Instead of increasing the yield of food crops, the aim of Dr Zhang's research is to create a self-sustained ecosystem in a closed environment that, food production under artificial scenarios will become feasible even in adverse environments like manned space station where has limited sunlight, and even make plantations possible in less favourable natural conditions.

用於人工光合作用的微流體技術：利用二氧化碳和太陽光生產食物原料

利用人工方法來增加糧食作物的產量，一直以來都是研究的熱點。而光合作用在農作物生產中，扮演著不可或缺的角色。然而，在植物產生糖和澱粉的過程中，自然光合作用的能量效率非常低（約1%）。限制因素主要有三個，分別是葉綠素將太陽中的綠光散射回去，浪費了綠色光的能量；大氣中的二氧化碳濃度很低（~420 ppm）；以及在天然光合作用中，關鍵型的催化酶（D-核酮糖-1、5-二磷酸羧化酶／加氧酶，簡稱RuBisCO）的活性和特異性較低。

應用物理學系副教授張需明博士開發了人工光合作用系統，以將二氧化碳直接轉化成可進一步加工為食品基本原料的葡萄糖前體。

張博士在研究中建造了多個能模擬天然光合作用的微流體平台，其中配備了可擴展的微反應器，以簡化捕光和酶催化反應。研究採用了能夠吸收可見光的半導體光催化劑（例如C3N4, Cu2O, Au／TiO2）來代替葉綠素，不僅能充份利用太陽光，亦更持久耐用。此外，張博士亦使用 NaHCO3 溶液來獲得更高濃度的二氧化碳，並在研究裡發現一步合成法，將RuBisCO固著到光催化劑上，可大幅提升酶的穩定性及重複使用性。只需使用非常少量的 RuBisCO，便足以顯著提升能量效率和酶活性，連續將CO2轉化為葡萄糖前體。

張博士的研究目標並非是要提升糧食作物的產量，而是希望在一個封閉的環境內，建造一個能夠自行持續運作的生態系統。即使在天然條件欠佳的高原、沙漠、遠海、載人太空站等環境下，亦能夠以人工方式生產糧食原料。